ENERGY EFFICIENT PROTOTYPE CLASSROOMDESIGN FOR SYDNEY, AUSTRALIA

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ENERGY EFFICIENT PROTOTYPE CLASSROOM

DESIGNFOR SYDNEY, AUSTRALIA

by

F elic ity Lew is

Copyright @ Felicity Lewis 1998

A Masters Report Submitted to the Faculty of the

College o f Architecture, Planning and Landscape Architecture

In Partial Fulfillment of the Requirements

For the Degree of

MASTER OF ARCHITECTURE

In the Graduate College

UNIVERSITY OF ARIZONA

1 9 9 8

St a t e m e n t by A u t h o r

This Masters Report has been submitted in partial fulfillment of requirements for an

advanced degree at the University of Arizona and is deposited in the University Library to

be made available to borrowers under rules of the library.

Brief quotations from this Masters Report are allowable without special permission,

provided that accurate acknowledgment of source is made. Requests for permission for

extended quotation from or reproduction of this manuscript in whole or in part may be

granted by the head of the major or the Dean of the Graduate College when in his or her

judgment the proposed use o f the material is in the interests of scholarship.

In all other instances, however, permission must be obtained from the author.

A p p r o v a l b y M a s t e r s R e p o r t C o m m i t t e e C h a i r m a n

This report has been approved on the date shown below:

Date

Director of Graduate Program

D e d i c a t i o n

To my Family, who have been through so much, these are the good times,

To my committee, Fred Matter, Susan Moody and Larry Medlin, thank you for your

support,

To all the faculty, staff and students at the U of A, College of Architecture, thank you for

making these three years memorable,

And especially to my friends....

3

Introduction

Few dispute the effects o f mankind’s dependence on energy derived from fossil fuels.

As we consume these non-renewable energy sources we are wrecking havoc on the

environment in which we live. The combustion of fossil fuels generates by-products that

are grouped under the label of “greenhouse gases”. These gases are now being produced at

such a rate they are affecting the air we breathe and the atmosphere that protects our

fragile planet.

The effects of these gases are manifold: they deplete the ozone layer whilst producing a

global warming situation, as the sun’s energy is trapped within the earth’s atmosphere. The

ozone layer protects the earth from galactic radiation and it’s depletion leaves the earth

vulnerable. Global warming increases the incidence of drought, reduces the earth’s ability

to produce food and melts the polar ice caps.

Australia is particularly vulnerable to these effects. As a country blessed with abundant

natural resources and large reserves of coal, oil and natural gas, it is heavily dependent

upon these resources for the generation of energy .Although other ecological problems are

assailing the planet, greenhouse gas emission is possibly the most potentially devastating

for Australia.

Australia is the driest continent in the world with two thirds o f the country classified as

arid or semi-arid. Drought is the most prevalent natural disaster, and although the land

area of Australia is equivalent to that of the continental United States of America, it is at

present only able to sustain a population equivalent to approximately 7%. Most of the 18

million people who live in Australia do so within the fertile coastal band.

The environmental picture is bleak: a hole has formed in the ozone layer off the south

coast of Australia; 1998 was declared the hottest year on record; the polar ice caps are

retreating at an increasing rate; and droughts and bush fires are increasing in frequency and

duration.

1

In response to this perceived disaster, Australia has led the world in alternate energy source

research. Study into the use of solar energy, in particular, has been intense over the last

thirty to forty years, with much of this research focused on developing energy efficient

housing. Housing has been considered the most important target for energy reduction due

to its prevalence as a building type and due to the wishes of many individuals who want to

make a difference.

The scale o f most housing is conducive to energy efficient techniques. Generally, the

building type is small in scale and low rise, and is usually occupied by a family, comprising

a small group of related individuals. There is also a direct connection between energy

usage and the financial cost of the energy used, so even if ecological concerns are not

paramount, cost savings are a strong inducement to reduce energy usage.

Energy efficiency has not been as rigorously or as thoroughly studied in other building

types, although this is changing. There is a growing base of information concerning the

translation o f results developed in housing into other building types.

Schools are a case in point. A school classroom is comparable in scale to most residential

developments, being small in scale, compartmentalized, often detached and low rise.

However, it does not have a comparable function or occupancy.

A classroom functions as a place where children can be educated, where they will learn to

read, write and explore their world. It is vital that this space is one in which they feel

comfortable, safe and happy. The occupancy of an average classroom is a teacher and

thirty to thirty five students. This can be a disparate group, coming from a wide range of

backgrounds.

In translating the advances made in energy efficient residential design to a classroom

situation, attention needs to be given to the differences in function and occupancy.

2

The effects of even small reductions in energy use at an individual classroom level can be

dramatic when considered at a national level. This is a situation where the adage “every

little bit counts” is most applicable.

Schools are significant consumers o f energy. They operate almost year round and are

occupied for a large part of the day. A breakdown of the sources of energy usage point to

lighting, at 50%, and heating and cooling, at 30%, as being the biggest energy consumers.

This report focuses on methods of reducing the consumption of energy produced through

the combustion of non-renewable resources.

The logical premise for this report was provided by the bioclimatic equation as proposed

by Szokolay1 and applied to the situation in Sydney, that:

Given Conditions - Comfort Conditions = Required Controls

The bioclimatic equation presents the relationship between the existing climate, the human

occupants of a space and the strategies that can be deployed to offset any incompatibilities

in this situation.

The first variable in the bioclimatic equation is the Given Condition. This encompasses

conditions, both cultural and physical, that influence the building being studied.

Culturally, Sydney is the biggest city in Australia, with a population of 4 million people. It

is located on the South East coast of the continent in the state of New South Wales. It is a

metropolitan city with a diverse population encompassing many different cultures. From

its beginnings as a British penal colony in 1788 it has flourished into an international city.

Climatically, Sydney is positioned within the temperate coastal zone protected to the

West by the Blue Mountains, a section of the Great Diving Range, and to the East by the

Pacific Ocean. Overall, the climate is not a severe one, although it does, at times, rate

outside the human thermal comfort range.

3

The second variable in the equation is the Comfort Condition. This variable needs to be

defined for both the visual and thermal environment.

The comfort conditions within a classroom do not vary widely from those that exist

within a house, or any other occupied space. The human body, although resilient, does not

have a large tolerance for climatic variation and in order for the body to perform at its

most efficient, these conditions narrow even further. This applies to both the visual and the

thermal environment.

The product of the equation are the Required Controls, and it is in relation to these

controls that energy efficient strategies are developed.

This report presents some possible strategies to employ in the fight to at least slow down

our societies head long plunge into environmental annihilation. 1

1 Szokolay, p329.

4

The Australian Education System

Table of Contents

History of Education in Australia 6

Current Educational Theories 9

Current Influences on Education 10

Evolution of the Modern Classroom 12

Endnotes 15

Table o f Figures

Figure 2.1: Lancastrian Monitorial System 7

Figure 2.2: Pupil-Teacher class layout 8

5

Australia has had an organized “western” education system from the time o f white

settlement, 210 years ago. From its beginning, as a means of instilling morality into the

young members of a penal colony, it has progressed to a system providing a bewildering

array of educational opportunities for all children between the ages of 4 and 16. The

system consists of a hierarchy of school levels; young children aged 4 to 8 attend Infants

School, those aged 8 to 12 attend Primary School, and those aged 12 to 16 attend High

School. Further education is available on an elective basis until the age o f 18, when

entrance into a University or other tertiary institution is often undertaken.

A wide range of schools are available. State (Public) schools are available at all levels, as are

private schools, run by denominational and secular agencies, the majority of these are

operated by the Catholic Church. All schools are eligible to receive state funding but must

be registered in order to do so. Eligibility for registration depends on the school fulfilling

State designed syllabus requirements.

This chapter provides an historical perspective of education in Australia. It also looks in

some detail at the substantial reforms to education methods which have influenced the

physical layout and design o f classrooms.

H i s t o r y o f E d u c a t i o n in A ustra l ia

When education was first established in colonial Australia, a system referred to as the

Traditional Individual method was used. All the students attending a school shared a

classroom, often a room in the school master’s house. The children were expected to study

silently at their desks, except for the three or four periods in the day when they would be

called to the teacher’s desk for individual attention. Due to its intensive one-on-one nature

this system could only operate while schools were small.

6

The next system of organized classroom instruction was the Lancastrian Monitorial

System. This was first introduced in Sydney in 1811, having been developed by Joseph

Lancaster, a Quaker, in 1798. Students still shared a single classroom or hall, but sat in

rows of about ten according to their academic level. A monitor was appointed to each row.

A single school master was responsible for explaining the learning process to the monitors,

who then explained it to the students. This system allowed schools to become

considerably larger. At this time teaching aids, in the form of maps and wall charts, began

to appear, and the reward and punishment system became formalized.

F ig u re 2 .1 : L a n c a s t r ia n M o n i to r i a l S y s t e m 1

In 1797, a rival monitorial system was developed by Dr. Andrew Bell, an Anglican

clergyman, and this eventually appeared in Sydney schools in 1820. Based on the Anglican

Church catechism, less emphasis was placed on reward and punishment, with promotion

to a higher grade being considered ample reward. The number of students per monitor

was also increased to twenty five.

In 1851, ‘Pupil-Teacher’ classes became popular. This system utilized apprentice, or pupil,

teachers in the classroom. All classes took place in one large classroom sub-divided into

smaller sections and students were divided into classes according to academic level. The

7

school master worked with one class at a time, while the remaining classes were attended

to by a pupil-teacher, who was supervised by the school master at all times.

B ° » .

' — 5 — ::

5

1 c \S k e tc h o f sc h o o lr o o m i l lu s tr a t in g tr ip a r tite m o n ito r ia l sy s te m in u s e in

th e d en o m in a tio n a l sc h o o ls ab ou t 1850.

A . T e a c h e r ’s d esk . C . D r a f ts fo r h e a r in g o r a l w o r kB . D e s k s an d F o r m s fo r th r e e b y te a c h e r s o r m o n ito r s ,

d iv is io n s . D . C u rta in s .

F ig u re 2 .2 : P u p i l - T e a c h e r class l a y o u t 2

All of these systems were evident in New South Wales schools during the years to 1906,

when a new ‘Probationary Student’ system, with its more formalized approach to teacher

training was introduced. The Probationary Student system was in use in New South Wales

from 1906 to 1913. The basic procedure was similar to that of the pupil-teacher system,

but had more formal state intervention. Trainee, or probationary, teachers had to pass an

examination to gain entrance to the newly established Teaching Colleges, and the

examination could be attempted only after two years of experience had been gained.

Changes to this system occurred in 1913, when the education system adopted the ideas

and methodologies of J. F. Herbart. Under his system individual teachers conducted

separate classes, and were required to receive training at a Teaching College prior to

becoming responsible for a class.

8

During the early 1970’s a new system of “open education” gained support in some

Australian States. There initially was some confusion about the true meaning of ‘open’,

with some exponents believing it meant an 'open-minded’ approach to education, while

others believed it referred to an ‘open school’, involving the community at large. The third

expression of this concept was the development of 'open classrooms’, where multiple

classes were taught in a single space. Team teaching became the norm in such situations,

classrooms were often clustered together and different projects were undertaken by

individuals or groups of students.

The system currently used in New South Wales schools is a combination of the above.

Some topics and subjects are taught by an individual teacher in a single, separate

classroom, while others are team taught in joint classrooms, using a more classic ‘open’

method.

C u r r e n t E d u c a t io n a l T h e o r i e s

Australian education has been influenced by many factors, including the need to balance

the educational aims of individuals with those of society; the curriculum required to

supply a liberal education and that desired for a vocational education; and the formal and

informal pedagogical methods of teaching.

Bassett et al3 used a classification system proposed by Kneller to organize current theories

on education. The terms perennialism, essentialism, progressivism, reconstructionism and

existentialism are used to differentiate between educational aims.

Perennialism emphasizes traditional intellectual values considered to have a universal and

permanent character. The major disciplines are considered the most important and a

knowledge of them is the basis for a liberal education.

9

Essentialism considers as essential knowledge pertaining to an individuals ability to cope

with his/her duties as a citizen. The method of teaching specific subjects derives from the

logic inherent in the subject, rather than from a study of the psychological needs of

children.

Reconstructionism is socially oriented, and views education as having a role in bringing

about social change. Supporters of this theory are wary of education becoming simply

indoctrination.

Progressivism, which has its roots in Europe, places its focus on the student, and stresses

the need to deal with each student as an individual. Problem solving and interest in the

subject are seen as essential ingredients for learning, the key concept being that education

is the continual reconstruction of experience. This theory has its greatest following in the

United States.

By contrast, existentialism, which also focuses on the individual, is largely a European

theory which seeks to counter the utilitarian nature of our age. Knowledge is considered to

have a definable nature, needing to be experienced directly in order to be learnt. This

theory is often encountered in fields outside education, such as literature and religion.

Current Australian theory is an eclectic mix of all the above doctrines, as no one theory can

encompass all the facets of education.

C u r r e n t In f lu en ce s o n E d u c a t i o n

When considering current influences on education it is necessary to consider the influence

of society itself. These influences can be divided into three categories: political; economic;

and sociological.

10

Politically, society has a need to raise children to be responsible adults with an

understanding of, and the skills necessary to partake in, a democratic society. Political

intervention and influence in education is two pronged in Australia, because of the federal

system of government. In New South Wales, the Federal (Commonwealth) Government,

and the New South Wales (State) Government both have jurisdiction.

Traditionally education is a state responsibility, but in an attempt to equalize the systems

operating nation wide, the Federal Government has become more involved, particularly in

the tertiary area.

Economically, Australia is a prosperous country, and there is a belief that the country can

offer a high level of education to the nations children. Consequently free, compulsory

education is provided to all children to the age of 16.

Australia’s prosperity has resulted in a trend towards vocationalism, and students are

expected eventually to be able to take their place in the work force, as productive members

of society. A growing shift in Australia’s employment pattern over the last fifty years has

seen a progression beyond rural production to industrial production as the primary source

of national income, and then to the post industrial phase, where workers are required to be

able to interact with consumers in a service situation.

Sociological patterns and needs are probably the most changeable and far reaching

influences on education. As a colonized nation, Australia is a country of immigrants.

Historically, most immigrants to Australia were European. However, the ethnic

background of immigrants has changed in recent years, and now the majority are Asian. In

1947, a mere 2% of children attending school were born in a non-English speaking

11

country. By 1971 this figure was 11%. It is now estimated that one child in seven comes

from a home where English is not spoken as the primary language4.

Equality of opportunity is one of the most dearly held maxims within Australian society,

and one of the hardest needs to satisfy. Efforts to equalize educational opportunities run

into the reality of the isolation of country students, the disparity between the States with

regards to funding, and the disparity between State and Non-State schools with regards to

the quality o f the education being provided.

The other significant sociological influence is that of the family. More and more families

are unwilling or unable to provide the support the educational system needs, as families

become more fragmented children must learn to deal with different types of home life. It

is becoming essential for schools to respond to the changes occurring within the day-to-

day life of the students.

E v o l u t i o n o f the M o d e r n C lassroom

Space usage in modern primary school classrooms is radically different from that seen in

the traditional classrooms discussed earlier. In the traditional classroom “instruction”5 was

emphasized. The teacher stood at the front of the room and student’s desks were arranged

facing the teacher. Aisles between the desks allowed for student access, but more

importantly facilitated the teacher’s supervisory role6. There was little contact with the

outside world, as it was considered irrelevant to formalized education.

The modern classroom has evolved from this rigid model, due to the changing role of the

teacher, a more active role required o f students and a departure from a rigid curriculum7.

12

The classroom environment is now significantly more flexible with moveable tables and

chairs, and although the teacher has a desk, sometimes all the students will be taught as a

group or children will be working individually or in small groups on selected activities.

Floor space has been cleared and now provides space for group activities. Equipment is

stored in specialized alcoves. Connections to the outside world are encouraged and

children will often leave the classroom to access shared school facilities, such as art rooms,

and to interact with the wider community.

The ultimate expression of this modern classroom is the ‘Open School’, where the entire

school is a large interconnected space. A more conservative system involves individual

classrooms that have the ability to become larger communal spaces, depending on the

needs of the subjects being studied. Where once classrooms formed a series of anonymous

doors along a corridor, emphasis is now placed on integrating all classrooms into a wider

school community.

Space usage in a modern primary school is a result of a series of decisions, both

philosophical and pragmatic in nature. Initially the decision must be made as to the

educational philosophy of the school. This directly influences the styles of teaching that

will be supported. The pragmatic decisions that flow from this revolve around issues of

curriculum (see Appendix A), school and class organization and class timetabling (see

Appendix B). All these issues will influence each other and affect how a class will be

conducted and how it will interact with the space in which it exists.

The more pragmatic issues of space usage relate initially to the physical facilities that are

available. Many schools are housed in buildings that were originally designed at a time

when educational methods were very different to what they are today. These physical

13

restrictions are often difficult to overcome and can have a significant influence on space

usage. W ithin these limits though, variation is possible.

14

E n d n o t e s 1

1 Barcan, p i7.2 Barcan, p i09.3 Bassett4 Bassett, p9.5 Bassett, p207.6 Bassett, p207.7 Bassett, p208.

Environmental Data and Classification

T ab le o f C o n te n ts

L ig h tin g D a ta 19

C loudiness and Sky Type 19

Illum inance Levels 21

L um inous E n v iro n m en t C la ss if ic a tio n 25

T h e rm a l D a ta 27

Air Tem perature 27

P recip ita tion 28

H um id ity 29

W ind 30

Insolation 31

C lim a tic C la ss if ic a tio n 32

E n d n o tes 35

16

Table o f F ig u res

Figure 3.01: Cloudiness o f Sydney skies 19

Figure 3.02: Occurrence o f specific sky types 20

Figure 3.03: Illumination levels : March 21st 22

Figure 3.04: Illuminance levels : June 21st 22

Figure 3.05: Illuminance levels: December 21st 23

Figure 3.07: Horizontal illuminance levels: according to sky type 24

Figure 3.06: Horizontal illuminance levels: % o f work year 24

Figure 3.08: Air Temperatures 27

Figure 3.09: Rainfall 28

Figure 3.10: Humidity 29

Figure 3.11: Wind Roses 30

Figure 3.12: Insolation 31

17

T his c h ap te r ad d re sses th e f ir s t co m p o n en t o f the b io c lim a tic d e s ig n

eq u a tio n .

In o rd e r to u n d e r ta k e a b io c lim a tic analysis o f a g iven lo c a tio n , ex is tin g

c lim a tic c o n d itio n s need to be d e te rm in e d . O n ce these have been

e s ta b lish e d , they can be an a ly zed to fo rm u la te an overview o f th e a c tio n

n eed ed to be tak en to achieve th e rm a l and visual c o m fo rt. T h e d a ta th a t

fo llow s in c lu d es the lig h tin g variab les o f c lo u d in ess , o ccu rren ce o f sky

ty p e , and illu m in an ce levels, and the th e rm a l c lim a tic variab les o f air

te m p e ra tu re , p re c ip ita tio n , h u m id ity , w ind and in so la tio n .

18

L i g h t i n g D ata

Cloudiness and Sky Type

T he fig u re below (F ig . 3 .0 1 ) g raphs the c lo u d in ess o f S y d n ey sk ies. T he

m ean m o n th ly c lo u d cover values, tak en tw ice d a ily , p ro v id e an in d ic a tio n

o f the a m o u n t o f c lo u d cover p re sen t in the sky . T hese values are m easu red

in e ig h th s , o r o c tas , o f the to ta l sky vau lt. I t is a p p a ren t th a t S y d n ey

ex p eriences p a r tly c lo u d y skies y ear ro u n d w ith , on average , ab o u t h a lf o f

the sky v au lt being co v ered . T h e re is som e seasonal va rian ce , w ith

m ax im u m c lo u d coverage being a p p a ren t in early a u tu m n (M arch and

A pril) and m in im u m cloud coverage o ccu rrin g in la te w in te r (A u g u st) .

O 2

£ 6 § §Months

9:00AM3:00PM

F ig u re 3 .01 : C lo u d in ess o f S y dney sk ie s1

19

T h e bar c h a r t b e lo w (F ig . 3 .0 2 ) d is p la y s the f r e q u e n c y o f o c c u r r e n c e o f

sp ec if ic sky ty p e s . T h is d a t a re la te s d i r e c t ly to th e p r e c e d in g c lo u d cover

d a t a , b u t p ro v id e s a m o re a c c u ra te in d i c a t i o n o f th e m e a n p e r c e n ta g e o f

the m o n t h th a t th e sky w ill be c lea r , th e p e r c e n ta g e it w ill be p a r t ly

c l o u d y , and the p e r c e n ta g e it w ill be o v e rc a s t , o r c l o u d y . T h e r e is n o t a lo t

o f an n u a l v a r ia t io n in sky c o n d i t io n s . C le a r sk ies o c c u r r o u g h ly 1 0 -1 $ % o f

th e m o n t h , a l th o u g h th is ju m p s to 2 5 -3 0 % in la te w in te r (Ju ly , A u g u s t ) .

C lo u d y skies o c c u r fo r a b o u t 1 0 -2 0 % o f th e m o n t h , y e a r r o u n d .

0)oc0)3ooO

>*oc<D3CT0)

1 0 0 %

90%

8 0 %

7 0 %

60 %

50 %

40 %

3 0 %

2 0 %

10%

0 % LH

1 1

□ cloudy

Q partly cloudy

■ clear

. ►. .... . .P

I I yM -i

M onths

F ig u re 3 .0 2 : O c c u r r e n c e o f sp ec if ic sky ty p e s 2

20

Illum inance Levels

T he fo llow ing fig u res in d ic a te the h o riz o n ta l illu m in an ce levels

ex p erien ced in S y d n ey . Illu m in an ce is the d e n s ity o f lu m in o u s flux

in c id e n t on a su rfa ce 3. T h is d a ta is p re sen te d in tw o fo rm s. T h e f ir s t set o f

figu res show d a ily values. T he n ex t se t show an nual values as a p e rcen tag e

o f the w o rk in g y ear.

T he f irs t set ( F ig . 3 .0 3 , 3 .0 4 , 3 .05 ) d isp lay the illu m in an ce levels u n d e r

the th ree sky types (c lear, p a r tly c lo u d y and c lo u d y ) fo r sp ec ific d a te s

d u rin g the year. F ig u re 3 .03 is the Spring S o ls tice , M arch 2 1 s t, F ig u re 3 .04

is the W in te r E q u in o x , June 2 1 s t, and F ig u re 3 .05 is the S u m m er E q u in o x ,

D e ce m b e r 2 1 s t. T hese th ree fig u res , w hen co n sid e re d to g e th e r , give a

co m p reh en siv e in d ic a tio n o f the c o n d itio n s ex p erien ced th ro u g h o u t the

year.

T he second se t ( F ig . 3 .0 6 , 3 .07 ) p lo t h o riz o n ta l illu m in an ce levels as a

p e rcen tag e o f the w o rk in g year. T hese values are used in d a y lig h tin g

d e sig n as th ey allow a value to be d e riv ed th a t w ill supp ly a sp ec ified

illu m in an ce level fo r a sp ec ified p e rcen tag e o f the w o rk in g y ear. F o r the

purpose o f these ch arts the w ork day was tak en as 9 :00 am to 17:00 pm .

F igure 3 .0 6 d isp lay s the annual average, w hile F ig u re 3 .0 7 show s the d a ta

a cco rd in g to sky ty p e .

21

o o o o o o o o o oo o o o o o o o o o

---------- Clear--------- p/Cloudy

---------- Cloudy

Time of Day

F ig u re 3 .03 : I l lu m in a tio n levels : M arch 2 1 s t4

Time of Day

F igu re 3 .04 : Illu m in an ce levels : June 2 1 s t5

22

---------Clear------- P/Cloudy

---------- Cloudy

o ▼-

Time of Day

F ig u re 3 .0 5 : I llu m in an ce levels: D e ce m b e r 2 1 s t6

23

100.0

90 .0

80 .0

7 0 .0

60 .0

5 0 .0

40 .0

3 0 .0<0 3 20.0

Diffuse Horizontal Illuminance (klx)

F igu re 3 .0 6 : H o riz o n ta l illu m in an ce levels: % o f w ork y e a r8

v r l 't r r A ivI'I'!4 1 4 'I 'I'I'It

Illuminance (klx)

---------- Clear

............ PartlyCloudy

—-------Cloudy

F igu re 3 .07 : H o riz o n ta l illu m in an ce levels: a cc o rd in g to sky ty p e 7

24

L u m i n o u s E n v i r o n m e n t C la s s i f i ca t io n

T he sky as a lig h t source is in f in ite ly v a riab le , as ev id en ced by the d a ta

p re se n te d . In o rd e r to in v es tig a te d a y lig h tin g s tra te g ie s it is necessary to

d e c id e upon a d e s ig n sky , w hich w ill specify lu m in an ce d is t r ib u tio n , and a

lu m in an ce level to be used fo r ca lcu la tio n s . T he values chosen need to

fu lf ill tw o c r ite r ia : the sky type needs to occu r o f te n en o u g h at th e site

lo c a tio n to be a valid cho ice ; and the lu m in an ce level need s to re su lt in a

re la tiv e ly low level o f in d o o r illu m in a tio n , usually the co d e m in im u m . T he

reason fo r these re s tr ic tio n s is so th a t the d a y lig h tin g values c a lc u la te d

from th is d e s ig n sky are ex ceed ed fo r the g re a te r p a r t o f th e t im e 9.

T he d e sig n sky chosen fo r S ydney is a In te rn a tio n a l C o m m iss io n on

I llu m in a tio n (C IE ) o v ercast sky. T h is c o n d itio n occurs o f te n en o u g h to be

valid and is the m o s t adverse o f the c o n d itio n s th a t p revail a t th is

lo c a t io n 10. T he d a ta p re sen te d in re la tio n to sky type (F ig . 3 .0 2 ) in d ic a te s

th a t a p a r tly c lo u d y sky w ou ld be a m ore obvious cho ice b u t a s ta n d a rd fo r

th is type o f sky has n o t been e s ta b lis h e d 11, so th e s ta n d a rd C IE overcast

sky is u sed .

T he d is tr ib u tio n p a tte rn fo r an overcast sky was e s tab lish ed by the C IE in

1955. I t was d e fin e d as a sky w here all p o in ts have a lu m in an ce equal to :

1 /3 L90 ( 1 + 2 sin x) w here L go = z e n ith lu m in an ce .

In rea lity the value used fo r L go is the illu m in an ce p ro d u c e d by the sky on

a h o riz o n ta l p lane ex posed to the w hole o f the sky and x = angle o f

a l t i tu d e .

25

Even th o u g h an o vercast sky c o n d itio n has been se le c ted fo r d e s ig n

p u rposes, o th e r possib le s itu a tio n s shou ld be c o n s id e re d . T w o o th e r

c o n d itio n s th a t are lik e ly are a c lear sky w ith less th a n 30% c lo u d cover

and a c lo u d y sky w ith b e tw een 30% and 80% c lo u d cover. T he

d is tr ib u tio n p a tte rn o f these skies w ill d if f e r from th a t o f the ov ercast sky.

T he lu m in an ce value fo r S y d n ey is se t a t 8500 lu x 12. T h e E x p e rim en ta l

B u ild ing S ta t io n 13 (EBS) fo llow s D re s le r and B ren tw ood in s e tt in g a lux

value th a t re su lts in d a y lig h tin g being su ff ic ie n t to p ro v id e the re q u ire d

lig h tin g levels, u n a id e d , fo r 90% o f the w o rk in g y ear. T h is co rre la te s w ith

the d a ta p re sen te d re la tin g to illu m in a tio n levels as a p e rc en ta g e o f the

w ork ing y ear (F ig . 3 .0 6 ).

F o r d a y lig h tin g ca lcu la tio n s the e ffe c t o f the sun is d is re g a rd e d , th is is

due to the fac t th a t as a lig h t source the sun has serious d raw b ack s. T he

v a riab ility o f d ire c tio n and the in te n s ity o f th e re su ltin g lig h t, w hich

resu lts in sharp shadow s and h igh c o n tra s t, is d e tr im e n ta l to m o st visual

tasks. G en era lly su n lig h t sh o u ld never fa ll upo n a ta sk p lane and w indow s

sh o u ld n o t be su n lit.

26

T h erm al D ata

A ir Temperature

T he fig u re below (F ig . 3 .0 8 ) shows the m ax im u m , m in im u m and m ean

m o n th ly te m p e ra tu re s ex p erien ced in S y d n ey . M ax im u m su m m er

te m p e ra tu re s usually exceed 2 5 °C . C o rre sp o n d in g m in im u m te m p e ra tu re s

average ab o u t 18°C . In w in te r the m ax im u m te m p e ra tu re s reach

a p p ro x im a te ly 1 7 .5 °C , w ith m in im u m s d ro p p in g to a p p ro x im a te ly 9 °C .

T he d iu rn a l (d a ily ) sw ing is on average ab o u t 1 0 °C , w ith the an nual sw ing

also being ab o u t 1 0 °C . T he ex trem es ex p erien ced can re su lt in

te m p e ra tu re s o f over 3 5 °C d u rin g su m m er, and ju s t above 0 °C in w in te r .

T he co asta l lo c a tio n o f S y d n ey has a m o d e ra tin g e ffe c t on its

te m p e ra tu re s .

3 0 .0 T

2 5 .0

20.0 -

d> 1 5 . 0 -

10 .0 -r

5. 0

o.o 4

Months

F igu re 3 .08 : A ir T e m p e ra tu re s 14

27

Precipitation

T he c h a rt below (F ig . 3 .0 9 ) d isp lay s the average m o n th ly p re c ip ita tio n

received in S y d n ey . R ain fa ll occurs y ear ro u n d , w ith a 60 m m d iffe re n c e

be tw een the m ax im u m and m in im u m m o n th ly values. T h e h ig h es t ra in fa ll

is re c o rd e d d u rin g the a u tu m n m o n th s o f M arch , A pril and M ay, w ith the

low est values being re c o rd e d d u rin g the sp ring m o n th s o f A u g u st,

S ep tem b er and O c to b e r . T h e re is a s ig n ific a n t d iffe re n c e in th e n a tu re o f

the ra in fa ll received d u rin g the y ear, su m m er ra in is acco m p an ied by fierce

s to rm s g e n e ra te d by h ig h te m p e ra tu re s and is to r re n tia l . In w in te r the ra in

is g e n tle r b u t p ro lo n g e d .

F igu re 3 .09 : R a in fa ll15

28

H um id ity

T he fig u re below (F ig . 3 .1 0 ) ch arts the average m o rn in g and evening

h u m id ity levels fo r S y d n ey , on a m o n th ly basis. As in d ic a te d , m o rn in g

h u m id ity levels are h ig h e r th a n evening levels, on average by 5% in

su m m er, and up to 15% in w in te r. T he h u m id ity level does n o t range

w id e ly th ro u g h o u t the y ear. T h e re is no d is t in c t season o f e x tre m e ly h ig h

h u m id ity , n o r is th e re a season o f very low h u m id ity , th is is d u e p a rtly to

S y d n e y ’s co as ta l lo c a tio n .

7 0 -

E 6 0 -

= 5 0

a 4 0 -

■3 3 0 -

2 0 -

1 0 -

Months

F igu re 3 .1 0 : H u m id i ty 16

29

W i n d

T he w ind roses below (F ig . 3 .11) in d ic a te the s t r e n g th , d i r e c t io n and

f requency o f w inds in S y d n ey . In su m m e r the p r e d o m in a n t w inds are from

the East. T hese are sea breezes and are m o s t w e lcom e w hen th ey occu r on

the a f te rn o o n o f a p a r t ic u la r ly h o t d ay . T he w o rs t w inds d u r in g th is season

are the “W e s te r l ie s ” , com ing o f f the ove rh ea ted in la n d , they are sco rch ing

h o t and ex ace rb a te a lread y ho t c o n d i t io n s . In w in te r the p r e d o m in a n t w ind

d i re c t io n is f rom the W es t , these are s till reasonab ly w arm , even at this

t im e , and m o d e ra te the coo ler te m p e ra tu re s o f th is season.

F igure 3 .11: W in d R oses17

30

I n s o l a t i o n

T he ch ar t below (F ig . 3 .12 ) d isp lays the in so la t io n th a t falls on b o th a

h o r iz o n ta l surface and a vertica l surface facing N o r th . T hese values

rep resen t the to ta l so lar r a d ia t io n s tr ik in g a su rface . T h is r a d ia t io n is

co m p rised o f th ree c o m p o n en ts : d i re c t ra d ia t io n from the sun; d if fu se

ra d ia t io n from the sky; and re f le c ted r a d ia t io n from the g ro u n d and

su r ro u n d in g b u i ld in g s 18.

2 0 -

n 15

Months

Figure 3 .12: In s o la t io n 19

C l im a t ic C la s s i f i ca t io n

C lim a t ic c lass if ica t io n allows c lim ates to be g ro u p e d acc o rd in g to specific

variables. N u m e ro u s system s o f c lass if ica t ion have been d e v e lo p ed in an

a t te m p t to c a teg o rize " the a lm o s t u n l im ite d c o m b in a t io n s o f c l im a tic

fac to rs a c ting on an a lm o s t in f in i te varie ty o f to p o g r a p h y ”20. T re w a r th a

believes this is d o n e so as to crea te o rd e r from “b ew ild e r in g m u l t ip l ic i ty ”21.

H aving labeled specific c lim a te types, it is possible to g en e ra te

co m m o n a lt ie s .

A n early system o f c lass if ica t ion d iv id e d the w orld in to five zones. T he

firs t zone was the T ro p ica l Z o n e , b o u n d e d by the T ro p ic o f C an c e r (23.5 °

N o r th ) , and the T ro p ic o f C a p r ic o rn (23 .5° S o u th ) , these b o u n d a r ie s are

the seasonal l im it o f the sun 's ve rtica l rays. T he nex t two zones , labeled

T e m p e ra te , occu r b e tw een the trop ics and the A rc tic and A n ta rc t ic C irc les

(66 .5° N o r th and S o u th ) , these b o u n d a r ie s d e f in e the l im its o f the su n ’s

ta n g en t ia l rays. T he fina l two zones are the P o la r Z ones , covering the

rem a in in g e a r th su rface22. T hese ca tego ries are d e f in e d by g en e tic

b o u n d a r ie s . T h ey are based on so lar i l lu m in a t io n , w hich is a cause o f

c lim a te . P re c ip i ta t io n was no t a govern ing variable and this resu lts in a

system th a t is too g en e ra l iz ed .

C lim a te s can be c a teg o r ized by g en e tic or causative fac to rs and by

em pir ica l or observable e ffec t . N e i th e r ap p ro ach w hen used exclusively can

give an accura te and c o m p le te view o f the varie ty p o ss ib le23. T re w a r th a puts

fo rw ard the b e lie f th a t a system th a t com bines the two app roaches w ou ld

32

be the m o s t accu ra te and useful. H ow ever, he also s ta tes th a t the em p ir ica l

shou ld always d o m in a te , fo r the g ene tic ap p ro ach can only supply

gen era lized p a t te r n s 24 . T h e re have been a n u m b e r o f c lass if ic a t io n system s

dev e lo p ed th a t a t t e m p t to com bine g en e tic and em p ir ica l app roaches .

T he m os t w id e ly accep ted o f these sys tem s was d ev e lo p ed by K oppen and

has u n d e rg o n e su b s tan tia l d e v e lo p m e n t since it f irs t ap p ea red in 1901. It is

fu n d a m e n ta l ly an em pir ica l c lass if ica t ion , because the c l im a tic types and

govern ing b o u n d a r ie s are g e n e ra ted by observed fea tu res o f te m p e ra tu re

and p re c ip i ta t io n and are no t co n s tra in ed in o rd e r to f i t w i th in a gen e tic

p a t te rn . H ow ever, m any o f the types do co in c id e w ith c e r ta in b ro ad -sca le

fea tu res o f a tm o sp h e r ic c ircu la t io n , w hich is a g en e tic d e t e r m in a n t25.

T rew a r th a has fu r th e r re f ined this sy s te m 26. T e m p e ra tu re and p re c ip i ta t io n

are the two p r im ary c l im a tic variables , w ith five o f the six c l im a tic g roups

being d e f in e d th e rm a lly , and the s ix th being d e f in e d by a r id i ty . These

g roups are:

Based on te m p e ra tu re c rite ria :

A. T r o p ic a l

C . S u b t r o p ic a l

D . T e m p e ra te

E. B o rea l

F. P o la r

Based on p re c ip i ta t io n c rite ria :

B. D r y

W ith in these p r im ary groups there are a series o f sub g roups , w h ich usually

p rov ide fu r th e r d iv is ions based on d is t r ib u t io n o f ra in fa l l27.

33

T he c l im a tic sym bols used in the T re w a r th a c l im a tic c lass if ic a t io n system

are l is ted in the A p p e n d ix (A ppend ix C ). T hese sym bo ls are d e f in e d by

specific physica l c o n d i t io n s . In c lu d e d in th is a p p en d ix are the c o n d i t io n s

govern ing the b o u n d a r ie s be tw een the zones.

A co m p ar iso n has been c rea ted to classify the c lim a te o f S y d n ey in to a

specific zone, this c o m p ar iso n is ta b u la te d in the A p p e n d ix (A p p en d ix D ) .

S y d n ey , is p laced in zone C f(a ) , acco rd in g to T r e w a r th a ’s sy s tem , this

in d ica tes it is w ith in the su b tro p ica l h u m id zone, it experiences no d is t in c t

d ry season and has ho t su m m ers .

H aving d e f in e d a c l im a tic c lass if ica t ion it is possible to in v es t ig a te the

b road e ffec ts o f c lim a te on b u ild in g design .

T h ere will be m ic ro c l im a tic varia tions app licab le to spec if ic sites. T he

fac to rs th a t will resu lt in v a r ia t io n in c lu d e the to p o g ra p h y , the surface

(g ro u n d ) c o n d i t io n and the su r ro u n d in g th ree d im e n s io n a l ob jec ts . These

issues need to be c o n s id e red s ite by s ite , as every s i tu a t io n will be

d if fe ren t .

34

E n d n o t e s

1 Ruck, 1985, p20.2 Ruck, 1985, p20.3 Ander, p222.4 Ruck, 1985, p37.5 Ruck, 1985, p37.6 Ruck, 1985, p37.7 Ruck, 1985, p42.8 Ruck, 1985, plO.9 Paix, p4.10 Paix, p4.11 Ruck, 1985, pl9.12 Paix, p5.13 Paix, p5.14 DA»SketchPAD2.0, www.arch.utas.edu.au15 DA»SketchPAD2.0, www.arch.utas.edu.au16 DA»SketchPAD2.0, www.arch.utas.edu.au17 Szokolay, 1987, pl9.18 Givoni, 1976, p38-3919 DA»SketchPAD2.0, www.arch.utas.edu.au20 Miller, p78.21 Trewartha, p238.22 Trewartha, p238.23 Trewartha, p242.24 Trewartha, p242.25 Trewartha, p245.26 Trewartha, p250-251.27 Trewartha, p250.

Visual Environmental Requirements

Table of Contents

Objectives of a lighting system 37

The Observer 38

How the eye sees 38

The Task 40

Tasks performed in a Classroom 40

Luminance of the task 41

The Lit Space 41

Illumination Level 41

Spacial Brightness Ratios 45

Glare 45

Conclusions 48

Endnotes 49

Table of Figures

Figure 4.01: Cutaway view o f the human eye 3 8

Figure 4.02: IES Recommended Illuminance Level 43

Figure 4.03: Recommended surface reflectances 4 4

36

The visual environment differs from the thermal in that vision is more than a physiological

response to stimuli. Vision occurs when the brain interprets images the eye is viewing. In

the thermal environment the body reacts as an organic organism, the brain does not

instruct the body to feel hot or cold, it is a physical manifestation of surrounding

conditions. In the visual environment, the external environment is filtered, the brain

compensates for, and adjusts, what the eyes see.

O b j e c t iv e s o f a l i g h t i n g system

The objectives of a lighting system must be primarily to provide for the safety of the

occupants of the space, and to “facilitate the performance of visual tasks”1, and “aid the

creation of an appropriate visual environment”2.

In determining what constitutes comfort conditions in relation to the visual environment,

it is necessary to consider the three interrelated components of the observer, the task and

the lit space. The observer is who sees, the task is what is seen, and the lit space supports

the seeing. Comfort when applied to the visual environment can more correctly be

considered the minimizing of discomfort. To provide an optimum situation in which to

perform visual tasks, it is necessary to eliminate or at least minimize circumstances that can

distract from the primary visual task.

37

T h e O bserver

H o w the eye sees

The mechanism of sight is a complex one, involving both the eyes and the brain. Lechner

uses the analogy of the “video camera of a robot”3 to explain the way in which the eye sees

and the brain interprets visual stimuli.

FOVEA

VITREOUS HUMORCORNEA

OPTICNERVE

Figu re 4 .01 : C u taw ay view o f the h u m a n eye4

In order to see, light must pass through the lens of the eye and strike the light sensitive

retina at the back of the eye. Mechanisms exist within the eye to control how much light

enters the eye and the focusing of this light on the retina. The pupil acts as an aperture

control, with the iris contracting and expanding depending upon the prevailing lighting

conditions. In very bright light the pupil contracts, limiting light access, whilst in dark

conditions the pupil expands, maximizing light infiltration. Focusing of light on the retina

occurs by way of manipulation of the shape of the lens, due to muscle contraction. The

38

retina is the light sensitive section of the eye that generates electrical signals that are then

transmitted to the brain for analysis.

Two types of nerve endings generate signals to the brain, namely rods and cones. Rods are

highly sensitive to the quantity of light present, and are utilized in low light situations.

They do not perceive color. Cones are the corollary, they operate most effectively at

normal light levels, and they see color. The differences in these receptors accounts for the

difference in nighttime, or scotopic, vision and daytime, or photopic, vision.

A further adaptation of the eye occurs due to the brain increasing and decreasing the

quantity of photo chemicals in the eye. With increased quantities of chemical the eye

becomes super sensitized to light and as the light levels increase the quantity of chemical is

reduced, resulting in de-sensitizing of the eye. Maximum quantities of the chemical can be

realized over the space of thirty minutes after entering a dark environment, the reversal of

this procedure requires about three minutes5. These changes occur in addition to the

physical changes occurring related to the size of the pupil. All of this explains the ability of

the eye to adapt to a wide range of brightness.

The other physical component of vision is the brain. Once the eye has received the light,

and transformed it into electrical signals, the brain then analyses these signals and perceives

what is being seen. Lechner extends his analogy of a robot, to include the concepts of “the

hardware (eye and brain) and the software (associations, memory and intelligence)”6.

Visual perception is the result of the brain analyzing what the eye sees. Perception involves

many complex interrelated concepts, but it fundamentally involves how the brain processes

information. Issues involved include the ability of an observer to focus on an object, and

isolate it from others, the ability to perceive a series of strokes of a pen on paper as words,

39

the ability to block out light color shifts, and the ability to perceive color and so on. This is

an area of study in and of itself, and beyond the range of this report.

The issue of importance in relation to the development of a suitable visual environment

relates to maximizing the eyes ability to receive information correctly. Information needs

to be relayed to the brain without conflicting images, or messages.

T h e Task

Tasks p e r f o r m e d in a C lassroom

With current trends in education, school classrooms are expected to cater for an ever

increasing variety of tasks, often being undertaken simultaneously. Whereas historically all

the children in one class would be undertaking one task at one time, be it reading, writing

or doing arithmetic problems, now children are likely to be involved in a myriad of tasks.

Some will be working at desks doing traditional tasks, others will be working on

computers, whilst others might be involved in activities such as painting and pottery.

The traditional visual tasks usually undertaken in a classroom have evolved as well.

Information is now provided in numerous ways, be it the teacher writing on the

chalkboard or the whiteboard, or students using newspapers, magazines, and computer

printouts. The use of multimedia has increased in classrooms, computers are increasingly

prevalent, as are televisions, videos, and projectors.

The lighting provided in today’s classroom needs to satisfy the visual requirements of all

these possible situations, and others that might arise in the future.

40

L u m i n a n c e o f the ta sk

Visibility relates to the ability of the observer to see a task. It is “the measure of the ease,

speed and accuracy with which the task may be seen”7. The visibility of a task depends on

a multitude of factors, including the luminance of the task, the contrast range of the task

and the adaptation requirements placed on the eye of the observer. The luminance of the

task refers to the brightness of the surface and is a product of the illuminance striking that

surface and the reflectance of the surface. Contrast is the relationship between the

luminance of a task and its background. A certain level of contrast is necessary for the eye

to differentiate the task, but too great a range can result in a reduced ability to discern

detail. Adaptation luminance is related to the physical ability of the eye to adapt to

changes in light levels and has been discussed above.

T h e Lit Space

The three main issues to be considered under the aspect of the lit space, are illumination

levels, spacial brightness ratios, and glare.

I l l u m i n a t i o n L e v e l

Lighting guidelines have been developed that provide recommended illuminance levels for

various tasks. These values are based on studies of the amount of light required to perform

specific tasks8. Some of these guidelines have been adopted as legal standards for the

provision of light in buildings. This is the case in Australia, where AS 1680.1-19909 Interior

Lighting Part 1: General Principles and Recommendations, covers all aspects of lighting

design including; task visibility, directional effects of lighting, surfaces, light sources,

lighting systems, and lighting design procedures. Subsequent parts of this standard

address lighting level requirements. These standards consider lighting design to be more

41

than just the provision of a certain lux level on a horizontal plane, requirements exist

concerning glare, unwanted reflectance and other quality issues.

The standard, AS 1680.2.3, sets the illuminance level for a general use classroom at 240

lux, and the value for a reading room classroom at 320 lux. These values are referred to as

a maintenance illuminance level, and although the issue of the maintenance of lamps,

luminaires and room surfaces is more directly related to electric lighting systems,

daylighting systems also suffer a loss of illumination level due to accumulated dirt on

glazing and room surfaces. A maintenance illumination level is the “value of average

illumination below which it is necessary to take remedial action in terms of maintaining

the lighting system”10.

In the United States of America, the IES (Illuminating Engineering Society of North

America) Lighting Handbooks are the most influential lighting guidelines. The IES

Lighting Handbook uses a different procedure to determine required illuminance levels11.

Initially an illumination category is selected from tables, based on the task being

performed. These categories provide a range of illuminance levels, the final level is decided

upon after a series of weighting factors are calculated. These factors include the age of the

viewer, the speed and accuracy requirements of the task, and the reflectance of the task

background. An example of this procedure, as applied to a classroom, is presented in the

figure below (Fig. 4.02). The resulting recommended illuminance level is in the range of

300 to 750 lux, depending on the specific task being performed. In proposing a procedure

that utilizes a range of illumination levels, the IES has sought to allow lighting designers a

level of flexibility and latitude in their final choice of lighting levels.

42

Illuminance Selection Procedure IE S (p 2 -4 )

Step 1:Define Visual Task

reading writing drawing, etc.

Step 2:Select Illuminance Category IE S F ig . 2 -1 (p 2 -5 )

Educational FacilitiesClassrooms - General see Reading

Reading

Illuminance Category D and E

Step 3:Determine Illuminance Range

D Performance of visual tasks of high contrast or large size

200 300 500

E Performance of visual tasks of medium contrast or small size

500 750 1000

Step 4:Establish Illuminance Target Value

Weighting Factors IE S F ig . 2 -3 b (p 2 -2 1 )

task background reflectance 30 - 70 % 0age of occupants under 40 -1importance of speed / accuracy important 0

If weighting factor total equals -1,0,+1 use middle illuminance values

Total -1

Recommended Illuminance value is 300 - 750 lux.

F igure 4 .02 : IES R e c o m m e n d e d I l lu m in an ce L evel12

43

The difference to be noted between the two documents is the variation in the lighting level

recommendations. The U. S. standard levels are significantly higher than the European

and Australian levels, and have always been so13.

In order to achieve the illumination levels discussed above attention needs to be given to

the reflectance’s o f the primary surfaces o f the room. The aim is to reduce the brightness

o f the brightest surfaces o f the room, whilst brightening the darkest ones. Castaldi14 and

others have suggested the following reflectance values: floors should be as light as possible

and practical, with a reflectance in the order o f 30 - 50%; walls should have a reflectance

o f between 40-60%; ceilings need to diffuse as much light as possible, and therefore need

a reflectance o f 70-90%; chalkboards, or the now more common whiteboards, need to be

as light as possible and furniture and fittings need to have a reflectance o f about 40%. The

figure below is a graphic representation of these values (Fig 4.03).

40-60%

UP TO 20%

40-60%

40-60%

30-50%

F i gu r e 4 . 03 : R e c o m m e n d e d s u r f ace r e f l e c t a n c e s 15

44

S p a c i a l B r ig h tn e s s R a t i o s

It is important to consider the balance of brightness that may be present within the field of

view of an observer when they are engaged in a visual task. Ratios are calculated in relation

to the brightness of the task when compared to the brightness of its surroundings.

Guidelines have been developed that minimize eye fatigue and maximize the observers

ability to undertake the visual task. These guidelines include:

• limiting the brightest surface to a value no more than ten times that of the poorest lit

task

• not letting any surface be of a brightness less than a third of the brightness of the

poorest lit task

• the brightness of any surface immediately adjacent to the task should not exceed the

brightness of the task, ideally adjacent surfaces should be about a third the brightness

of the task

• and minimizing the difference in brightness of adjoining surfaces16.

G la re

Glare is defined as “[a]ny brightness within the field of vision which causes discomfort,

annoyance or interference with vision”17.

The standard, AS 1680.1-1990, sets a maximum glare index for specific spaces that a

lighting system must satisfy. For school classrooms the maximum glare index is 1918. This

value is in the middle of the range of values, that rise in value from 13, for extremely

exacting visual tasks, to 28, which is the value applied to rough or intermittent tasks

requiring little glare control.

Glare can occur in a number of forms. Direct glare occurs where there is a light source in

the observers field of view, specular glare results when there is a specular reflection in the

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observers field of view, and contrast glare is created when an extremely bright object is

seen against a dark background.

The most obvious sources of direct glare are windows. A number of strategies are possible

to reduce the possibility of glare occurring. These include the use of tinted low

transmission glazing, providing light colored surfaces adjacent to the window, providing

additional lighting directed to the surfaces adjacent to the window, and the use of

adjustable louvers19. When dealing with glare from electric lighting the standard specifies

two alternative methods to evaluate it, one being the luminaire selection system, the other

being the glare evaluation system20. The most obvious solution is to either remove all light

sources from the field of vision of an observer, or provide shielding so that the source is not

directly visible.

Specular glare can be controlled by careful attention to the use of finishes on room

surfaces. Highly reflective surfaces will give rise to specular reflections, diffuse surfaces will

not. Choice of a diffuse lighting system, where light is diffused off the ceiling is another

option. Care also needs to be given to the choice of materials for the task, reflective glossy

papers can result in veiling reflections.

Veiling reflectance is a form of specular glare that occurs on the surface of the task, rather

than within the observers field of vision. They occur when light sources reflect off the task,

into the eyes of the observer, effectively obscuring the task. To avoid veiling reflectance the

material being used for the task should not be glossy, and light sources should be avoided

in positions where they might bounce light into the viewers eyes. Light crossing from the

side of the task avoids this problem.

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The issue of contrast glare can be addressed by attending to the juxtaposition of elements.

Very bright areas should not be placed adjacent to dimmer areas. The use of narrow beam,

direct light sources should be avoided.

Due to the varied nature of the activities that can occur in a primary school classroom it is

necessary to create a lighting system that will provide adequate light levels for all

occasions. The solution is to use a combination of ambient lighting, to provide an overall

level of light, and task lighting, to supply supplementary lighting as required. The ambient

lighting level will be the illuminance level as set by code, the task lighting will be in

addition to this. The provision of light and therefore the layout of the lighting system

should not dictate the way a classroom is used. Desks are rarely placed in a formal

arrangement, more often they are moved around as required, therefore there is a need for

the ambient lighting system to provide a uniform light distribution over most of the

classroom floor area. Supplementary lighting is needed where the ambient light level is

inadequate, this is likely to occur at the perimeter of the room, as it is here that many

teachers establish alcoves dedicated to certain activities, such as reading and computer

usage. In order to eliminate visual discomfort a ratio of 0.8 must be maintained between

the maximum and minimum illuminance levels in the space21.

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C o n c l u s i o n s

The above has been an overview of the requirements of a suitable visual environment. The

lighting provided in a classroom needs to be more than merely functional, in fact to design

such a system,

“is to ignore the fact that

...poor lighting can impair vision , cause general body fatigue, and increase

body tension. Too long concentration on close tasks, without the exercise

of distant viewing, causes eye fatigue and strain. A tired, tense student

cannot respond alertly to the learning activities and the schoolroom “22.

Primary school children can spend up to six hours a day, five days a week for nine months

of the year in a classroom, the visual environment created in the space they occupy is

obviously going to influence their well-being. A visual environment needs to be created

that is stimulating, and supportive of the educational agenda.

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E n d n o t e s

1 AS 1680.1 - 1990, plO.2 AS 1680.1 - 1990, plO.3 Lechner, p257.4 Kaufman, 1984 VI, p3.2.5 Szokolay, 1980, p88.6 Lechner, p258.7 AS 1680.1 - 1990, pl2.8 Robbins, p26.9 AS 1680.1 - 1990.10 AS 1680.1 - 1990, p9.11 Kaufman, 1987 V2, p2.3.12 Kaufman, 1987 V2, p2.4.13 Robbins, p27.14 Castaldi, p282.15 Kaufman, 1981 VI, p6.4.16 Castaldi, p281.17 Sleeman, p i46.18 AS 1680.1 - 1990, p37.19 AS 1680.1 - 1990 p36.20 AS 1680.1 - 1990, p36.21 AS 1680.1 - 1990, p i7.22 O’Connor, p i82.

49

Thermal Environmental Requirements

T ab le o f C o n te n t s

O b jec tives o f a c o n d i t io n in g system 51

T he O c c u p a n t 53

H u m a n Response 53

T he B u ild ing B ioc lim atic C h a r t 58

T he T h e rm a lly C o n d i t io n e d Space 62

Air T e m p e r a t u r e 62

H u m i d i t y 63

Air M o v e m e n t 64

R a d i a t i o n 65

Use o f Space 67

C onc lu s io n s 67

E n d n o tes 68

T ab le o f F ig u r e s

F igure 5 -0 1 : T h e rm a l B alan ce o f th e H u m an B o d y 5 3

F igure 5 -0 2 : B u ild in g B io c lim a tic C h a r t f o r S y d n e y , A u s tr a l ia 6 0

F igure 5 -0 3 : B u ild in g B io c lim a tic C h a rt, w ith c o n tro l zo n e s 61

50

This c h ap te r will d iscuss the e n v iro n m en ta l re q u ire m e n ts th a t are necessary

to achieve a c o m fo r ta b le in d o o r th e rm a l en v iro n m e n t .

T he th e rm a l c o n d i t io n s th a t occu r w ith in a space e lic it a b io log ica l

re a c tio n from the o ccupan ts o f th a t space. T he h u m a n b o d y can only

survive w ith in a l im ite d range o f c o n d i t io n s and can only fu n c t io n at its

m os t e f f ic ien t w ith in an even m ore specific range . F o r c h i ld re n to pe rfo rm

at th e ir peak p o te n t ia l , c o n d i t io n s w ith in the c lassroom will id ea lly fall

w ith in th is zone o f o p t im a l p e rfo rm an ce .

O b j e c t iv e s o f a c o n d i t i o n i n g system

A n o p t im a l th e rm a l e n v iro n m en t is achieved w hen the h u m a n b o d y is able

to fu n c t io n e f f ic ien tly . T h is occurs w hen the p o in t is reached at w hich

m in im a l e x p e n d i tu re o f energy is req u ired for the b o d y to a d ju s t to its

e n v iro n m en t. In re la t io n to schools and the p rov is ion o f an o p t im a l

learn ing e n v iro n m en t, this p o in t can also be d e f in e d as the one w hich is

conducive to “a ler t , a t te n t iv e and m o t iv a te d ” 1 s tu d e n ts .

T he p rov is ion o f sy stem s, e i th e r active or passive, th a t are d e s ig n e d to

m o d e ra te the th e rm a l e n v iro n m en t m us t in no way “ im p e d e the fu n c tio n a l

or h u m an is t ic needs o f the s tu d e n ts and te a c h e rs”2 th a t in h ab it the space.

T he p rim ary fu n c t io n o f a c lassroom space is to su p p o r t the learn ing

experience .

T he objectives o f a c lassroom th e rm a l c o n tro l system m u s t be to p rov ide a

th e rm a l e n v iro n m en t conducive to learn ing . In o rd e r to evaluate the

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effectiveness o f such a system it is necessary to c o n s id e r th ree aspec ts , the

o ccu p an t o f the space, the in te ra c t io n o f the th e rm a l variab les , and the

space itse lf .

D ue to the fac t th a t “c o m fo r t is d e te rm in e d p r im ari ly by the ra te o f

exchange o f heat b e tw een an in d iv id u a l and his e n v i ro n m e n t”3, the

o ccupan ts o f a space will be the m a jo r d e te rm in a n ts o f th e rm a l c o m fo r t .

T h e rm a l re g u la t io n o f the b o d y ’s te m p e ra tu re is a response to ex te rn a l

s t im u li . It is n o t a reasoned response , bu t an o rg an ic one.

T h ere are m u lt ip le variables th a t in te ra c t to achieve re su l ta n t th e rm a l

c o n d i t io n s . T he m o s t obvious o f these are air te m p e ra tu re , h u m id i ty and

v en ti la t io n . M ean ra d ia n t te m p e ra tu re is less obvious bu t equally crucial. A

n u m b e r o f m e th o d s have been d eve loped w hereby the in te ra c t io n o f these

variables can be c o n s id e red and c h a r te d . Extensive research has been

u n d e r ta k e n th ro u g h o u t the w orld to es tab lish th e rm a l c o m fo r t ind ices .

All energy t ran s fe r is governed by the laws o f th e rm o d y n a m ic s .

T he f irs t law o f th e rm o d y n a m ic s is the p rinc ip le o f energy . E nergy

can n o t be c rea ted or d e s t ro y e d bu t only co n v er ted from one form to

a n o th e r ” .4

T he second law o f th e rm o d y n a m ic s ... s ta tes th a t h ea t (or energy )

t ran s fe r can take place sp o n tan eo u s ly in one d i re c t io n only : f rom a

h o t te r to a coo ler b o d y or, genera lly , from a h ig h e r g ra d e to a low er

g rad e s t a t e ” .5

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T hese laws o p e ra te so as to m a in ta in a s ta te o f th e rm a l n e u tra l i ty , be it

w ith in a b u ild in g in re la t io n to c o n d i t io n s o u ts id e , o r a h u m a n b o d y in

re la t io n to its e x te rn a l en v iro n m en t.

T h ere are th ree m e th o d s o f h ea t transfe r ; c o n d u c t io n , co n v ec tio n and

ra d ia t io n . C o n d u c t io n is “ the sp read in g o f m o lecu la r m o v e m e n t

th ro u g h o u t an o b jec t or ob jec ts in d i re c t c o n ta c t”6. C o n v e c t io n “is the

fo rm o f hea t t ra n s fe r from the surface o f a solid b o d y to a f lu id , i .e ., a

l iqu id or gaseous m e d iu m ”7. R a d ia t io n is the em ission from a surface o f

energy in the fo rm o f in fra - red w aveleng ths .

T h e O c c u p a n t

H u m a n R es p o n s e

± C n d

F igure 5 .01: T h e rm a l Balance o f the H u m a n B o d y 8

53

The h u m a n b o d y acts like o th e r ob jec ts do in re la t io n to h ea t t ra n s fe r and

the m a in te n an c e o f th e rm a l e q u il ib r iu m . T h e rm a l ba lance ex ists i f the

fo llow ing e q u a t io n h o lds true :

M E T - EVP + .C N D + .C N V +.RAD = 0

“M E T ” refers to m e ta b o l ism , or “ the b io log ica l processes w i th in the b o d y

th a t lead to the p ro d u c t io n o f h e a t”9. T h is occurs e i th e r as basal

m e ta b o l ism , w hich is the c o n s tan t d ig e s t io n o f fo o d in to energy , or

m uscu lar m e ta b o l ism , w hereby the use o f m uscle p ro d u ces hea t as a

b y p ro d u c t o f w ork .

“E V P ” refers to ev apora tion . T h is is the process w hereby h ea t is los t from

the b o d y by the a p p lic a t io n o f heat to t ra n s fo rm a liqu id in to a gaseous

fo rm . Sw eating is an exam ple o f th is , as is b rea th in g .

“C N D ” refers to c o n d u c t io n . This is e i th e r a hea t ga in or a h ea t loss

process, as energy is t ran s fe r re d from a w arm o b jec t to a co o le r one by

d i re c t c o n ta c t . H e a t ga in will occur i f the b o d y is in c o n ta c t w ith a surface

th a t is w a rm er and heat will be lost i f the b o d y is in c o n ta c t w ith a surface

th a t is coo ler .

“C N V ” refers to convec tion . In this process heat is ga ined or los t to a

su r ro u n d in g f lu id w hich is usually air. As for c o n d u c t io n , th is process

occurs acco rd in g to the second law o f th e rm o d y n a m ic s .

54

“R A D ” refers to r a d ia t io n . T h is process occurs w hen an o b je c t ra d ia te s

in fra - red energy , w hich s tr ikes a n o th e r ob jec t . W h e th e r th is resu lts in a

heat ga in or loss will d e p en d on the re la tive te m p e ra tu re s o f the ob jec ts

and th e ir p ro x im ity . T he h u m an b o d y acts as an o b jec t in re la t io n to

ra d ia t io n .

In n o rm a l c ircu m stan ces , a s e d e n ta ry person in a c o m fo r ta b le c lim a te will

lose h ea t from the b o d y in th ree ways. A p p ro x im a te ly 45% will be lo s t

th ro u g h ra d ia t io n , 30% will be lost th ro u g h con v ec tio n and 25% th ro u g h

e v a p o ra t io n .10

In o rd e r to susta in life the h u m an core b o d y te m p e ra tu re m u s t rem a in

w ith in a very narrow range. T his m u s t occur rega rd le ss o f the f lu c tu a t io n s

in e x te rn a l e n v iro n m en ta l co n d i t io n s .

T he skin is the o rgan th a t is d ire c t ly responsib le fo r m o d u la t in g the b o d y ’s

te m p e ra tu re . T he ideal skin te m p e ra tu re is a m a t te r o f personal p re fe rence

b u t is usually in the range o f 31 to 3 4 °C , and “sk in te m p e ra tu re can be

m a in ta in ed only i f a ba lance exists be tw een hea t in p u t to the skin and the

heat loss, or o u t p u t ”11

A core b o d y te m p e ra tu re o f 3 7 °C is n o rm a l. A n u m b e r o f causes can resu lt

in a change in b o d y te m p e ra tu re , in c lu d in g a change in the ex te rn a l

te m p e ra tu re , or in the m e ta b o l ic ra te o f heat p ro d u c t io n . I f hea t is n o t

d is s ip a ted su ff ic ien tly , the skin reacts by d i la t in g the b lo o d vessels close to

the skin surface , increasing heat t ran s fe r to th is surface and th e reb y

enhancing ra d ia n t and convective heat d is s ip a tio n . I f th is proves

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in su ff ic ien t and the b o d y te m p e ra tu re co n tin u es to rise, sw eating will

occu r w ith its assoc ia ted evaporative cooling e f fec t . H y p e r th e rm ia resu lts

if these m easures c o n tin u e to be in su ff ic ien t to re s to re hea t ba lance and

heat s troke can occu r as the b o d y te m p e ra tu re reaches 4 0 ° C . I f it reaches

4 2 °C d e a th is in e v i ta b le .12

T he o p p o s ite scenario involves a “hea t d is s ip a t io n ra te [ tha t] exceeds the

heat p ro d u c t io n r a t e ”13. T he sk in now reacts via v a so c o n s tr ic t io n in o rd e r

to slow the tra n s fe r o f hea t to the surface o f the skin, w h ils t low ering skin

te m p e ra tu re . R a d ia n t and convective hea t d is s ip a t io n is now d im in is h e d .

T he in su la t io n ac t io n o f the sk in tissue is enhanced b u t f ro s t b ite can occu r

at the e x tre m it ie s due to a lack o f b lood flow. I f th is proves ine ffec tive

shivering occurs, w hich p ro d u ces a m uscu lar m e ta b o l ic re a c t io n w ith

assoc ia ted heat p ro d u c t io n . I f these m easures fail to b ring the b o d y back

to a s ta te o f th e rm a l balance h y p o th e rm ia can occur. D e a th is inev itab le if

the b o d y te m p e ra tu re d ro p s to be tw een 2 5 °C to 3 0 °C .

O ne succ inc t d e f in i t io n o f th e rm a l c o m fo r t as it re la tes to h u m a n b o d y

core te m p e ra tu re is p ro v id ed by Szokolay .

“T he l im its o f ex is tence can be d e f in e d in te rm s o f d e e p -b o d y

te m p e ra tu re as ly ing be tw een 35 and 4 0 ° C , the n o rm a l be ing ab o u t

3 7 °C . T he skin te m p e ra tu re m us t always be less th a n the d e e p -b o d y

te m p e ra tu re , as hea t is to flow in th a t d i re c t io n . T h e te m p e ra tu re o f

the e n v iro n m en t in tu rn m u s t be below the sk in te m p e ra tu re , i f heat

is to be d is s ip a te d . T he range o f e n v iro n m en ta l te m p e ra tu re s th a t

will a llow su ff ic ien t , bu t no t excessive hea t d is s ip a t io n , and will

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th e re fo r be ju d g e d as “c o m fo r ta b le ” , is re fe rred to as the co m fo r t

zo n e ” 14

Even th o u g h the re are de f in ab le physica l l im its to the d e f in i t io n o f th e rm a l

c o m fo r t , in rea li ty the p e rc ep t io n o f c o m fo r t occurs a t an in d iv id u a l level.

In d iv id u a l ch arac te r is t ic s a f fec t in g th e rm a l c o m fo r t in c lu d e the ac tiv ities

being u n d e r ta k e n , the q u a n t i ty and na tu re o f the c lo th in g being w orn , and

the a c c l im a tiz a t io n o f the b o d y 15. T he ab il i ty o f an in d iv id u a l to in fluence

all b u t the last o f these ch arac te r is t ic s m akes exac t d e te r m in a t io n o f an

ideal in d o o r c lim a te im possib le . T he e n v iro n m en ta l fac to rs can be

m a n ip u la ted to w ard s o p t im a l c o n d i t io n s su ited to the m a jo r i ty o f the

occu p an ts , b u t rare ly will it be possible to su it everyone.

D e te r m in a t io n o f o p t im a l th e rm a l c o n d i t io n s will also be in f lu en ced by

cu ltu ra l hab its . T he ways in w hich the space is u sed , the c lim a te to w hich

the o ccupan ts are a cc lim a tized and the a t t i tu d e o f socie ty to w ard s the

th e rm a l en v iro n m e n t will all be fac to rs . In genera l, the use o f air

c o n d i t io n in g and cen tra l h ea tin g is u n c o m m o n in S y d n ey , th e re fo re

socie ta l hab its are a d a p te d to this .

T h e rm a l c o m fo r t zones have been d eve loped th ro u g h the use o f em p ir ica l

e x p e r im en ts , som e o f the m o s t ex tensive o f w h ich were c o n d u c te d by

F a n g e r16. In these s tu d ie s the in itia l ex p e r im en t used A m e ric an college

s tu d e n ts as sub jec ts . S u bsequen t tests to v a lida te these f in d in g s were

p e r fo rm ed using b o th D an ish college s tu d e n ts and e ld e r ly persons as

sub jec ts . S ta t is t ic a l d a ta from these s tu d ie s p roved th a t a d u l ts te n d to

react s im ila rly to the th e rm a l en v iro n m en t, regard less o f age or

57

n a t io n a l i ty 17. W h e n co n s id e r in g the a p p lic ab il i ty o f these f in d in g s to an

e n v iro n m en t where the o ccupan ts will be a lm o s t exclusively ch ild re n ,

F anger concedes th a t “ [ f ]u r th e r w ork is n eed ed on c h i ld re n ” 18

T h e B u i l d i n g B i o c l i m a t i c C hart

O ne o f the ear lies t a t te m p ts to fo rm alize the idea o f th e rm a l c o m fo r t as it

re la tes to e n v iro n m en ta l variables was p u t fo rw ard by O lg y a y in his book

D esig n w ith C lim ate™ . T he c u lm in a t io n o f this process re su lted in a

“b io c l im a tic c h a r t” , w h ich in d ic a te d a c o m fo r t zone an d , fo r c o n d i t io n s

o u ts id e this zone, p ro p o sed necessary a d ju s tm e n ts th a t cou ld be

u n d e r ta k e n . T he c o m fo r t zone is d e te rm in e d by the in te ra c t io n o f d ry bulb

te m p e ra tu re and re la tive h u m id i ty . T h e re is an a ssu m p tio n th a t the re is no

air m o v e m e n t and no ra d ia n t heat ga in or loss. T he s t ra teg ie s fo r the

a d ju s tm e n t o f non c o m fo r t zone c o n d i t io n s focus on e i th e r the a d d i t io n o f

sunshine ( r a d ia n t heat) o r w ind (air m o v em e n t) . T h e re fo re th is ch ar t allows

s im u ltan eo u s c o n s id e ra t io n o f the fo u r p r im ary th e rm a l variab les .

G ivoni h ig h l ig h te d p rob lem s o f the O lg y ay m o d e l , c la im ing th a t it was

“ l im ited in its a p p l ic a b i l i ty ”20, due to the fact th a t “ the analysis o f

phys io log ica l req u ire m e n ts is based on the o u td o o r c lim a te and n o t on th a t

ex p ec ted w ith in the b u ild in g in q u e s t io n ”21. H e asserts th a t “ the re la t io n

o f in d o o r to o u td o o r c o n d i t io n s varies w ide ly w ith d i f f e r e n t ch arac te r is t ic s

o f the b u i ld in g c o n s t ru c t io n and d e s ig n ”22.

T he a l te rn a te m e th o d p roposed by G ivoni is based on the In d ex o f

T h e rm a l Stress, w hich is “a b iophysica l m o d e l d esc r ib in g the m echan ism s

o f heat exchange be tw een the b o d y and the en v iro n m e n t , f rom w hich the

58

to ta l th e rm a l stress on the b o d y (m e tab o lic and en v iro n m e n ta l) can be

c o m p u te d ”23. A n analysis o f the c lim a te is u n d e r ta k e n in i t ia l ly , fo llow ed by

the d e v e lo p m e n t o f a B u ild ing B ioc lim atic C h a r t . T h is ch ar t allows the

d e s ig n e r to observe the s im u ltan eo u s e ffec t o f m u lt ip le variab les . T he

B uild ing B ioc lim atic C h a r t is p lo t te d on a p sy c h ro m e tr ic char t .

T he p sy ch ro m e tr ic char t is a char t used to d ia g ram the in te r re la te d

variables a ffec t in g th e rm a l c o n d i t io n s . T he six p sy c h ro m e tr ic variab les

are:-

D B T - d ry bulb te m p e ra tu re is an in d ic a to r o f sensible hea t, or the heat

c o n te n t o f p e rfec t ly d ry air.

W B T - w et bulb te m p e ra tu re is an in d ic a to r o f the to ta l hea t c o n te n t (or

en th a lp y ) o f the air, th a t is, o f its co m b in ed sensible and la te n t

heats .

A H - abso lu te h u m id i ty is d e f in ed as the w e ig h t o f w a te r vapor

co n ta in ed in a un it vo lum e o f air.

RH - re la tive h u m id i ty is d e f in e d as the (d im en s io n less ) ra t io o f the

a m o u n t o f m o is tu re c o n ta in ed in the air u n d e r spec if ied c o n d i t io n s

to the a m o u n t o f m o is tu re co n ta in ed in the air at s a tu ra t io n a t the

sam e (d ry bulb) te m p e ra tu re .

H - e n th a lp y is the sum o f sensible and la te n t heat c o n te n t o f a

p a r t ic u la r a tm o sp h ere re lative to th a t o f the 0 °C air.

sv - specific vo lum e is the rec ip rocal o f d en s i ty .

In o rd e r to u tilize this char t as a B uild ing B ioc lim atic C h a r t it is necessary

to locate the c o m fo r t zone as d e te rm in e d fo r the p a r t ic u la r c lim a te u n d e r

59

s t u d y . Sz o ko l a y o u t l i n e s a m e t h o d to achieve thi s (see A p p e n d i x E) . T h e

f i gure be l ow (Fig . 5 . 02) is the Bu i l d i n g B i o c l i ma t i c C h a r t fo r S y d n e y .

30

!0 2 5 ;Dry Bulb Temp: deg C.

Is85

D Thermal Comfort Zone

F i gu r e 5 .02: B u i l d i n g B i o c l i m a t i c C h a r t for S y d n e y , A u s t r a l i a

A d d i t i o n a l ca l c u l a t i o n s to p o s i t i o n s t r a t e g y zones are neces sa ry to

c o m p l e t e the Bu i l d i n g B i o c l i m a t i c C h a r t (see A p p e n d i x E). T h e s e zones

q u a n t i f y the e f f ec t s o f var ious s t r a t eg i e s , n a m e l y pass ive so la r h e a t i ng ,

mass e f f ec t , mass e f f e c t w i t h n i g h t v e n t i l a t i o n and the e f f e c t o f i nc r e a sed

air m o v e m e n t . T h e f i gu re be l ow (Fig. 5 .03) o u t l i n e s these zones .

60

r: g

/ k<

30

10 25 cDry Bulb Temp: deg C.

Thermal Comfort Zone [ _i Mass Effect

' ; Passive Solar Gain H Air Movement Effect

S '

I183

F i gu r e 5 .03: Bu i l d i n g B i o c l i ma t i c C h a r t , w i t h c o n t r o l zones

T h e a d v a n t a g e s o f an i n t e g r a t i ve s y s t e m over s ingle f i gu r e i n d i ce s are

m a n i f o l d . T h e t h e r m a l e n v i r o n m e n t is the r esu l t o f the i n t e r a c t i o n o f

m u l t i p l e var i ab les , so a p r e d i c t i o n m e t h o d t h a t c o n s i d e r s these

i n t e r r e l a t e d issues wi l l prove m o r e ac c u r a t e and m o r e f l ex i b l e t h a n a

s ys t em t h a t c a n n o t i n t e g r a t e these var i ables s i m u l t a n e o u s l y .

T h e B u i l d i n g Bioc l im a t ic C h a r t c o n s id e r s the e n v i r o n m e n t a l var i ab les bu t

is unab l e to f a c t o r in the i n d i v i d u a l f ac t o r s o f ac t i v i t y level , c l o t h i n g and

m e t a b o l i c ra t e . F o r this r ea son t he re wil l a lways be a l eeway n e e d e d to

a c c o m m o d a t e the i n d i v i d u a l p r e f e r enc es o f as m a n y o c c u p a n t s as poss ib le .

61

T h e T herm al ly C o n d i t i o n e d Space

I t has been d e te rm in e d th a t “physica l s tam in a and m e n ta l a c tiv ity are at

th e ir best w ith in a g iven range o f c lim a tic c o n d it io n s ”24.

W h en co n sid e rin g the th e rm a lly c o n d itio n e d space in te rm s o f d e fin ab le

variab les the fo u r p rim ary ones are a ir te m p e ra tu re , h u m id ity , a ir

m o v em en t and ra d ia tio n . Each o f these can be q u a n tif ie d and th e ir e ffe c t

m easu red th e re fo re , th ey can be m a n ip u la ted so as to o ffse t un fav o rab le

c lim a tic c o n d itio n s , th ro u g h the use o f s tra te g ic d e sig n .

A i r T e m p e r a t u r e

T he te m p e ra tu re o f the a ir has the m o st d ire c t e ffe c t on h u m an c o m fo rt.

A ir is the m ed iu m w ith w hich the sk in is in d ire c t c o n ta c t, a lb e it th e re is

o f te n an in su la tin g lay er o f c lo th es p re sen t.

T he air te m p e ra tu re needs to be a t a level w here it w ill su p p o rt the h um an

h eat balance e q u a tio n . T he tw o hea t c o n tro l p rocesses e ffe c te d by air

te m p e ra tu re are co n v ec tio n and ev ap o ra tio n and in a s e d e n ta ry person

these can p ro v id e up to 55% o f the b o d y 's h ea t loss. As sk in te m p e ra tu re is

usually b e tw een 31° and 3 4 °C , the air te m p e ra tu re needs to be a t a level

w hich allow s the b o d y to d iss ip a te hea t if it needs to , via b lo o d vessel

d ila tio n (co n v ec tio n ) and sw eating (ev ap o ra tio n ).

T es ta reco m m en d s a c lassroom air te m p e ra tu re o f 18° to 2 2 ° C 25. T hese

te m p e ra tu re s are a l i t t le low er th an those in d ic a te d by the B u ild ing

B io c lim atic C h a r t , w hich are w ith in the range o f 18.5° to 2 2 .5 °C ,

d e p en d in g on the asso c ia ted h u m id ity .

62

E ffective te m p e ra tu re (ET) is a n o th e r m easure o f te n ap p lied to a ir

te m p e ra tu re . ET is d e f in e d as “ the te m p e ra tu re o f a s till , s a tu ra te d

a tm o sp h e re , w h ich - in the absence o f ra d ia tio n - w ou ld p ro d u c e the sam e

e ffe c t as the a tm o sp h e re in q u e s tio n ”26. T h is in d ex co n sid e rs the fac to rs o f

d ry bulb te m p e ra tu re , w et bulb te m p e ra tu re and air v e lo c ity . C o rre c te d

e ffec tiv e te m p e ra tu re (G E T ) in c lu d es the e ffe c t o f ra d ia tio n by ex ch an g in g

the g lo b a l te m p e ra tu re fo r d ry bulb te m p e ra tu re in the c a lcu la tio n s .

T he re c o m m en d e d a ir te m p e ra tu re needs to be m a in ta in ed in the zone o f

space o ccu p ied . V a ria tio n s in te m p e ra tu re can o ccu r d u e to th e e ffe c t o f

co n v ec tio n , w hereby h o t air w ill rise and co o ler a ir w ill s e tt le , b u t th is

v a ria tio n needs to be lim ite d to a less th an 3° te m p e ra tu re sh if t , o therw ise

th e re w ill be a big d iffe ren c e b e tw een the te m p e ra tu re s o f the head and

fee t and re su ltin g d is c o m fo rt.

H u m i d i t y

H u m id ity has a d ire c t e ffe c t on the ev ap o ra tio n ra te th e b o d y can achieve.

As a m easure o f the a m o u n t o f w a ter vapor co n ta in ed in the a ir, w hen

h u m id ity is h igh the a ir has a red u ced a b ility to absorb m ore w a te r , thus

ev ap o ra tio n is re d u c e d .

T es ta reco m m en d s m a in ta in in g re la tive h u m id ity w ith in the range o f 50% -

6 0 % , the B u ild ing B io c lim atic C h a r t c o m fo rt zone covers a range o f

re la tive h u m id ity from 2 0 -9 0 % .

63

E x trem es o f h u m id ity are p ro b le m a tic . T h is is p a rtic u la r ly th e case w ith

h igh h u m id ity in excess o f 9 0 % , due to the fac t th a t e v ap o ra tio n all b u t

ceases w hen the air is s a tu ra te d as it can no lo n g e r abso rb a d d it io n a l w a ter.

T he b o d y uses ev ap o ra tio n as a m ajo r h eat re g u la tio n p rocess. I t is also an

e ffic ie n t m e th o d o f hea t re g u la tio n at the b u ild in g scale, ev ap o ra tive

coo lers rely on th is process to p e rfo rm th e ir co o lin g fu n c tio n .

D e h u m id if ic a tio n is n o t possib le w ith o u t the in te rv e n tio n o f chem ica l

d esiccan ts or m ech an ica l e q u ip m e n t, so excessive h u m id ity is one c lim a tic

c o n d itio n th a t can n o t be a m e lio ra ted by the d e sig n o f the b u ild in g .

Low h u m id ity te n d s to o ffse t the e ffec ts o f h igh te m p e ra tu re s . T h e b o d y

can increase sw eat p ro d u c tio n , w ith a c o m m e n su ra te increase in

ev ap o ra tio n to m o d e ra te the e ffec ts o f h ea t.

A i r M o v e m e n t

T he ra te o f air m o v em en t in a space e ffec ts the co n v ec tio n and ev ap o ra tio n

p rocesses. C o m fo rta b le ra tes o f a ir m o v em en t are o f te n d e te rm in e d by

fac to rs o th e r th an th e rm a l c o m fo rt and lim its are usually based on the

need to red u ce the in c id en ce o f the m o v em en t o f pap er.

A n o th e r issue th a t can a ffec t the se lec tio n o f a su itab le ra te o f a ir

m o v em en t is th a t o f the need fo r a ir w ith in a space to be c irc u la te d and

in fused w ith fresh air so as to d ilu te o d o rs th a t w ill occu r as a re su lt o f

sw eating and ex h a la tio n . D u rin g re sp ira tio n the h u m an b o d y g en era te s

64

carb o n d io x id e , w hich is th en ex h a led . T h is th e n m u st be rep laced w ith

o x ygen o r the a ir w ill ra p id ly becom e u n b re a th ab le .

C a s ta ld i re co m m en d s 10-15 f t 3 o f fresh a ir per s tu d e n t per m in u te 27, w hich

fo r a class o f th ir ty s tu d e n ts , equates to 3 0 0 -4 5 0 f t 3 or 8 .5 -1 2 .7 5 m 3 per

m in u te . T h is is p rim arily req u ired fo r o d o r rem oval, and fresh a ir su pp ly ,

ra th e r th a n fo r th e rm a l reasons. T es ta has a su g g es ted ra te o f a ir m o v em en t

o f less th a n 1 m per se c o n d 28 as an air speed fa s te r th an th is can blow

papers a ro u n d and w ill g en era lly cause a d is tu rb a n c e w ith in th e class.

R a d i a t i o n

R a d ia tio n , o r th e release o f in fra -re d energy by an o b je c t o r su rface , is the

h a rd e s t o f all variab les to ca lcu la te and re g u la te . M ean ra d ia n t te m p e ra tu re

(M R T ) is “ the a rea -w e ig h ted m ean te m p e ra tu re o f all s u rro u n d in g

su rface s”29 and p rov ides the m o st co m m o n ly used in d ex o f ra d ia tio n . T h is

te m p e ra tu re is m easu red using a g lobe th e rm o m e te r th a t read s g lobe

te m p e ra tu re (G T ). T h is is equal to M R T w hen th e re is no air m o v em en t.

T he re la tio n sh ip o f G T to D B T in d ic a te s w h e th e r ra d ia tio n is p ro d u c in g a

hea t ga in or a h ea t loss in re la tio n to the th e rm o m e te r . A h ea t ga in w ill

re su lt in a G T h ig h er th a n the D B T , w h ils t a h ea t loss w ill p ro d u c e a G T

low er th an the D B T 30.

R a d ia tio n is d ire c tio n a l, it is e m itte d o r ab so rb ed in to a su rface , the ra te

a t w hich the su rface ra d ia te s or absorbs energy being d e p e n d e n t on the

surface m a te ria l as w ell as on the presence o f energy sources. E x te rn a l

envelope su rfaces are exposed to so lar ra d ia tio n w hich in tu rn is abso rb ed

in to the m a te ria l and possib ly re -ra d ia te d e ith e r e x te rn a lly o r in te rn a lly .

65

T he cho ice o f d ire c tio n is d e te rm in e d by the laws o f th e rm o d y n a m ic s as

p rev iously d e sc r ib e d . I f the su rface is co o ler th a n the space and the ob jec ts

w ith in it, energy w ill be a b so rb ed . I f the reverse occurs energy w ill be

re leased .

R a d ia tio n h ea t loss in a sed e n ta ry p e rso n eq u a tes to 45% o f h ea t loss, a

s ig n ific a n t p a r t o f the b o d y ’s hea t reg u la to ry p rocesses. F o r th is to o ccu r

su rro u n d in g su rfaces need to be co o ler th an the b o d y .

T he d ire c tio n a l n a tu re o f ra d ia tio n can resu lt in unequal ex p o su re if one or

m ore su rfaces are s ig n ific a n tly h o tte r or c o ld e r th an o th e rs . T h e m o st

co m m o n exam ple o f th is is co ld w indow s, w here glass p ro v id es l i t t le

in su la tio n value and the g lazed su rface becom es very co ld and can absorb

hea t from anyone s ta n d in g nearby .

C lose p ro x im ity to a h o t su rface can deceive the b o d y ’s h ea t sensors in to

tr ig g e rin g a h eat response a lth o u g h the b o d y , as a w ho le , is n o t

ex p erien c in g h ea t o v e rlo ad . T he o p p o site re a c tio n can be tr ig g e re d by

p ro x im ity to a co ld su rface w hereby the b o d y reacts w ith co ld responses

even if the b o d y is in fac t a t balance.

It has n o t been d e fin itiv e ly d e te rm in e d if a sy m m etr ica l ra d ia tio n has a

d e le te r io u s e ffe c t on the b o d y ’s th e rm a l c o m fo r t31. Som e s tu d ie s have

show n th a t te s t su b jec ts do exp erien ce d is c o m fo rt w hen ex posed to sh o rt

te rm a sy m m etr ica l ra d ia tio n . O th e r s tu d ie s , espec ially those involv ing

p ro lo n g ed ex p o su re , show ed li t t le ev idence o f d is c o m fo rt . O v era ll,

d isp a ra te ra d ia tio n levels from the surfaces asso c ia ted w ith a s ing le space

66

shou ld be av o id ed , b u t m in o r v a ria tio n s are un lik e ly to cause s ig n ific a n t

th e rm a l c o m fo rt concerns.

Use o f S pace

T he b ig g est e ffe c t th a t the use o f space in a c lassroom can have on the

in d o o r th e rm a l e n v iro n m en t is the v a rie ty o f a c tiv itie s th a t can occu r.

C h ild re n can be engaged in q u ie t a c tiv itie s like re a d in g , o r th ey can be

involved in m ore active ac tiv itie s such as d ance and d ra m a .

T he n u m b er o f c h ild re n in a c lassroom can vary d u rin g th e d ay , as can the

n u m b er o f c h ild re n involved in p a r tic u la r ac tiv itie s . C o n tro l o f the th e rm a l

e n v iro n m en t m u s t th e re fo re res id e in the c lassroom its e lf so th a t the

te ach e r can a d ju s t the c o n d itio n s as the s i tu a tio n changes. C o n tro l does

n o t necessarily im ply an active sy stem . Passive sy stem s to m a in ta in th e rm a l

c o m fo rt can be m an ip u la ted as easily .

C o n c l u s i o n s

O ’C o n n o r, p a rap h ras in g A ck erm an , su cc in c tly s ta tes the reason fo r the

necessity o f a th e rm a lly balanced c lassroom , w hen he w rites th a t:

“A n o v e rh ea ted ch ild is p rone to have lapses in c o n c e n tra tio n on

acad em ic m a tte rs and to relax and d a y d re a m . T h e re is som e

in d ic a tio n th a t s tu d e n ts m ay experience a 2% re d u c tio n in learn in g

a b ility fo r every d eg ree th a t the room te m p e ra tu re rises above the

• ) ) 32o p tim u m

A n u n d e rh e a te d ch ild w ou ld no d o u b t su ffe r as g re a t a d ro p in

p e rfo rm an ce as one who is o v e rh e a te d , so it is im p o r ta n t to m a in ta in a

s te a d y , o p tim a l th e rm a l en v iro n m en t in the c lassroom in o rd e r to

m ax im ize the learn in g e n v iro n m en t.67

E n d n o t e s

1 O’Connor, p i94.2 O’Connor, p i97.3 Castaldi, p266.4 Szokolay, 1980, p254.5 Szokolay, 1980, p254.6 Szokolay, 1980, p255.7 Szokolay, 1980, p256.8 Szokolay, 1980, p270.9 Szokolay, 1980, p270.10 Ballinger, 1997, p35.11 Szokolay, 1980, p270.12 Szokolay, 1980, p271.13 Szokolay, 1980, p271.14 Szokolay, 1980, p272.15 Konya, p26.16 Fanger17 Fanger, p86.18 Fanger, p86.19 Olgyay20 Givoni, 1976, p310.21 Givoni, 1976, P311.22 Givoni, 1976, P311.23 Givoni, 1976. p90.24 Olgyay, p i4.25 Testa, p39.26 Szokolay, 1980, p276.27 Castaldi, p21.28 Testa, p27.29 Szokolay, 1980, p259.30 Szokolay, 1980, p259.31 Fanger, p96.32 O’Connor, pl95.

68

BasecaseD esign

Table of Contents

Prototype Design 71

Home Base 76

Practical Activities Area 79

Withdrawal Room 82

Storage 84

Personal Effects Storage 86

Analysis of Prototype 88

Table of Figures

Figure 6.1: Home Base plan 72

Figure 6.2: Home Base cross section 72

Figure 6.3: Home Base longitudinal section 72

Figure 6.4: Home Base 7 6

Figure 6.5: Practical Activities Area 79

Figure 6.6: W ithdrawal Room 82

Figure 6.7: Storage 84

Figure 6.8: Personal Effects Storage 8 6

69

The basecase selected for this study is one of the Component Design Range (CDR) of

classrooms designed by the New South Wales Department o f Public Works and Services.

This home base block was chosen because it was a self contained group of classrooms that

could be analyzed as a single entity.

The home base block consists of two home base classrooms and a shared withdrawal space.

Each classroom has separate, attached, auxiliary spaces including a general storage area, a

personal effects storage area and a practical activities area. The classrooms are separated by

an operable wall which can be retracted when required to create a single space.

The total area of this home base block is approximately 200 m2. The areas of each distinct

part are as follows:-

home base classroom 57 m2

practical activities area 21 m2

withdrawal area 12 m2

storage area 8 m2

personal effects storage 4 m2

70

P r o t o t y p e D e s ig n

Part of the Schools Facilities Standard is reproduced here, and provides the educational

specifications o f the Primary School Facilities Standard as related to a Learning Unit,

which is composed of the learning space and associated spaces

The following provides a general overview of the Learning Unit, the activities that will

occur in each of the associated spaces, the spaces and requirements for each area, and the

relationships that need to be created between spaces.

Overall the Learning Unit caters for a wide range of experiences and activities appropriate

to the student’ stage o f development. Students will be working in many different media,

often simultaneously. A variety of relationships between teachers and students, both

formal and informal, will occur. Groups will range from individuals to a whole class or

grade.

Normally, the number o f classes grouped would be sufficient to allow a full Grade to work

as a unit. Experience has shown that pupil numbers have created variations to the accepted

standard of two (or three) classes per grade. There may be four Yr. 3 classes and only two

Yr. 4s, yet both grades need to be able to work together. To cater for these variations,

Plome Bases should be clustered in groups.

The activities that will occur in these spaces suggest the need for a variety of spaces and a

maximum of flexibility. The design should, as far as possible, be responsive to change and

not restrict the needs of future users.

71

General considerations to be addressed include the need for comfortable conditions for

class groups in clustered spaces.

Display of student’s work and other material is very important as it encourages the users to

personalize the Learning Unit. Display surfaces, both hanging and pinned on walls and

ceiling, should be provided wherever possible.

Following pages:

F igure 6 .1 : H o m e Base p lan

F igu re 6 .2 : H o m e Base cross sec tio n

F igure 6 .3 : H o m e Base lo n g itu d in a l sec tio n

72

3000mm

I

7670mm

w

5690mm 3970mm

1560mm 7675mm

Sharedf|thdra\lvaliRoonrl

Practical Activities i Area i

ivitiesPractical Actji i Area i

P700 mmSpringing Height

-P̂

uaue

i

^ 2 7 0 0 mm________Springing Height

O FFL

(VI

E 3

>

H o m e Base

G en era l

The Home Base is the core o f the Learning U nit and should be regarded as its most vital

element. It must accommodate a class of 30-35 students and their teacher, and provide an

identity for the group.

%%%%%%%%%

ee •,

F ig u r e 6.4: H o m e Base

76

Act iv i t ies

Organization may be formal or informal, with students sitting at desks facing a

chalkboard, or engaged in group or individual work spread throughout the room. Basic

skills are developing through opportunities for students to communicate, to investigate

and to express and at the same time to acquire knowledge, understandings, attitudes and

values.

Some of the activities that will occur in this space are:-

• Speaking and listening

• Observing and investigating

• Discussions

• Choral and instrumental music

• Poetry, story telling

• Drama, mime, plays, dance

• Incidental art / craft activities

• Free play with structured materials, toys

• Using A / V and computer resources

S paces / R e q u ir e m e n ts

• Approximately square shaped room is preferable to allow for both formal and informal

teaching approaches.

• A centrally located chalkboard or whiteboard positioned away from glare sources so

that all parts of the room have good visibility.

• Display is particularly important in the Home Base and maximum provision should be

made. Brown out is required for daytime A. V. work. Special consideration is needed

where sky lights are proposed.

77

• Acoustic absorption in the form of a soft floor finish to overcome noise from

movement is encouraged for informal teaching. This can also serve as an additional

learning surface where students can sit or sprawl when reading or listening.

• Acoustic separation between Home Bases is necessary to permit independent operation

of individual classes.

R e la tio n sh ip s

Wide openings are required between the adjoining Home Bases o f each Learning Unit to

give free movement and allow for supervision when classes combine and cooperate for

various activities. In a three Home Base cluster such openings are required between one pair

only. Where clusters of four are used, consider this as two pairs of two.

78

P r a c t i c a l A c t i v i t i e s A r e a

G enera l

An area is required for practical activities which can be an extension o f the Home Base.

F i g u re 6.5: P r ac t i ca l Ac t i v i t i e s Area

79

Act iv i t ies

This space provides an area where wet or messy activities can be undertaken by individuals

or small groups. A whole class group may be extended into the Home Base or the covered

outdoor learning area.

Activities may include:-

• Use of hand tools such as saws, hammers

• Printing with screen or block

• Modeling in clay, plaster, papier-mache

• Keeping birds, animals, insects

• Making props, costumes for plays

• Preparing, cooking and eating food

S paces / R e q u ir e m e n ts

Activities require:-• Water and drainage, and washing facilities

• Power

• Work benches

• Specialized equipment such as portable oven and boiling hot plate

• Easily cleaned surfaces

• Floor that is non-slip when wet

R e la tio n sh ip s

A Practical Activities Area should be provided and considered as an extension of the

Home Base. Where used, clusters of two or four Home Bases could have a shared Practical

Area. Each Home Base should have wide access to a Practical Activities Area for easy

80

communication and supervision. Many of the activities could well be carried on out of

doors. Direct access to the Covered Outdoor Learning Area from the Practical Area

provides potential for group or individual withdrawal, as well as direct contact with the

external environment.

81

W i t h d r a w a l R o o m

G en era l

An area is required for small groups o f students to occupy, away from the general student

space.

F ig u r e 6.6: W i t h d r a w a l R o o m

82

Act iv i t ies

This space will be used by small groups for a variety of activities. The noisy activities may

include discussions, poetry or drama readings, story telling and record or music playing.

The quiet activities may include individual study and reading.

S paces / R e q u ir e m e n ts

• Maximum free floor area and a minimum of furniture

• Soft floor finish

• Power outlets, MATV outlet

• Brown-out from external light

• Adequate ventilation to cater for groups using the space

R e la tio n sh ip s

A Withdrawal Area is required to separate small groups from the class in the Home Base.

This allows them to carry out activities which may be noise producing or which may

require a quiet area. The Withdrawal Area could be a room shared by 2 Home Bases, but

acoustically separable from them, or an alcove extension of the Home Base. Supervision of

activities in the Withdrawal Area should be possible from the Home Base.

83

S to r a g e

G enera l

A space for general purpose storage.

F ig u r e 6.7: S to r ag e

84

A c t iv i t ie s

This is to provide storage for materials and equipment used by teachers and pupils of one

Home Base and, in particular, allows the teacher to store items of personal equipment.

S paces / R e q u ir e m e n ts

Maximum use of the space and easy movement of mobile equipment should be aimed for,

e.g., by outward opening door. Some adjustable shelving is required.

R e la tio n sh ip s

• Direct access from Home Base is required.

• Easy access to Practical Activities Area.

85

P e r s o n a l E f f e c t s S to r a g e

G enera l

This space is for the storage o f student’s personal effects.

F ig u r e 6.8: Pe r s ona l Ef f ec t s S t o r a ge

Act iv i t ies

Storage is required for pupil belongings, in particular, bags and coats.

S paces / R e q u ir e m e n ts

Teachers will need to be able to supervise these facilities from the Home Base to ensure

security and assistance especially for younger children. Bags will require shelving for 30

children. Coats will require hooks and can be located externally, near the Practical

Activities Area entry. If internal a “wet” floor will be required to allow for dripping.

R e la tio n sh ip s• Extension of the Practical Activities Area

• Close to Home Base for direct supervision.

Separation o f bags and coats is required to reduce congestion.

87

Analys is o f P r o t o t y p e

The classroom and practical activities areas form a single open plan space that share a

cathedral ceiling. A bulkhead brings the ceiling height to 2700mm in the storage areas.

The materials used to construct this block are standardized. The floor is a slab on ground.

Carpet is used in the classroom spaces, withdrawal space and storage areas, while vinyl is

used in the practical activities areas.

The walls are brick veneer to a height of 2700mm, with a single external layer of face brick

and a steel stud internal load bearing layer. Above 2700mm, the walls are stud framed and

clad with a vertical metal deck. Insulation is added to these sections of the wall. The

internal wall finishes vary between a plasterboard lining and pinboard material.

The roof is metal deck with a plasterboard internal lining. Roof insulation is double

layered, with a 50mm thermal insulation layer laid directly below the metal deck and a

75 mm thermal insulation layer being laid directly above the plasterboard ceiling lining.

The space between these layers is vented using openings provided at the eaves and

ventilators at the ridge line.

Each classroom has windows to the south. The practical activities areas and the withdrawal

space having windows to the north, There are no windows in the east and west walls, apart

from small glazed panels inset into the access doors in these facades. All windows have a

common head height of 2143mm. Sill heights vary, with windows located in the north

facade having a sill height of 772mm, whilst the windows in the south facade have a sill

height o f 943mm. All windows are operable horizontal sliding units, with the openable

area being equal to half the total window area. These windows are shaded for part of the

year by a 900mm overhang created by the roof eaves.

88

Provisions have been made for daylighting in this design. In addition to the substantial

north and south facing windows, skylights have been inserted into the gable roof. These

take the form of strip roof lights, created by replacing half a sheet of roof metal deck with

a corrugated reinforced polyester translucent roof sheeting. This allows a clear span of

190mm of light access. Directly below this is a polycarbonate structured clear sheet, and in

the ceiling plane, a 400mm wide clear prismatic diffuser allows the light to enter into the

space and prevents direct sunlight access. These roof lights are possible because o f the use

of a cathedral ceiling and exposed roof trusses.

Fluorescent lights are installed to augment the daylighting strategies and to provide

illumination in non-daylit spaces such as the storage areas. These fittings are fixed to the

underside of the ceiling and integrate well with the position of the roof lights.

A number of thermal strategies have been employed. The large equatorial facing (north)

windows act as solar collectors, providing heating. The concrete slab has the potential to

act as mass storage, but this is not realized as the slab is covered in part by carpet and in

part by vinyl, both of which serve to insulate the slab. Gas fired heaters are provided in the

space, to offset cold conditions.

The cathedral ceiling has a cooling effect as it allows the warmer air to rise into this

volume, away from the lower occupied space. The roof ventilators remove this heated air,

whilst also ventilating the roof space. Air is drawn into the roof space at the eaves and

vented at the ridge, adding to the already well insulated roof. A total of six ceiling fans are

provided to allow for increased air movement if conditions become too warm. The

windows are shaded for part of the year and have internal Venetian blinds which can be

angled to offset solar penetration. No shading is provided for the roof lights, but the use

of multiple layers of polycarbonate acts to insulate these openings. Although the outer skin

89

of this building is brick, a massive material, due to the insulating action o f the steel stud

inner layer, it does not act as a mass storage material.

90

Visual Strategies

Table of Contents

Required Controls 94

Building Occupancy 94

Lighting Approaches 95

Electric lighting 95

Light Sources 95

Lighting Strategies 100

Daylighting 104

Daylighting Sources 105

Calculation Methods 106

Daylighting Systems 108

Daylighting Strategies 123

Endnotes 135

91

Table of Figures

Figure 7.01: Comparison o f Lamp Types 9 6

Figure 7.02: Comparison o f Luminaire Types 9 9

Figure 7.03: Lumen M ethod calculations 102

Figure 7.04: Glare Index calculations 103

Figure 7.05: Energy Usage in schools 104

Figure 7.06: Types o f Daylight 1 0 6

Figure 7.07: Proportional relationship ratios 108

Figure 7.08: Ratio variables - Window 111

Figure 7.09: Penetration curve - Window 112

Figure 7.10: Ratio variables - Clerestory 113

Figure 7.11: Penetration curve - Clerestory 114

Figure 7.12: Ratio variables - Horizontal aperture 1 1 6

Figure 7.13: Penetration curve - Horizontal aperture 117

Figure 7.14: Ratio variables - Angled aperture 118

Figure 7.15: Penetration curve - Angled aperture 118

Figure 7.16: Ratio variables - Sawtooth system 119

Figure 7.17: Penetration curve - Sawtooth system 120

Figure 7.18: Ratio variables - M onitor system 121

Figure 7.19: Penetration curves - M onitor system 122

Figure 7.20: Lighting curves - Basecase (with windows) 124

Figure 7.21: Photograph o f Base case ( with windows) 125

Figure 7.22: Lighting curves - Basecase (without windows) 125

Figure 7.23: Photograph o f Basecase (without windows) 1 2 6

Figure 7.24: Photograph o f Basecase ( without windows) 1 2 6

Figure 7.25: Location o f light sensors 128

Figure 7.26: Ratio variables - Sawtooth 129

92

Figure 7.27: Lighting curves - Sawtooth ( with windows) 130

Figure 7.28: Lighting curves - Sawtooth (without windows) 130

Figure 7.29: Photograph o f Sawtooth strategy 131

Figure 7.30: Photograph o f Sawtooth strategy 131

Figure 7.31: Ratio variables - M onitor 132

Figure 7.32: Lighting curves - M onitor ( with windows) 133

Figure 7.33: Lighting curves - M onitor ( without windows) 133

Figure 7.35: Photograph o f M onitor strategy 134

Figure 7.34: Photograph o f M onitor strategy 134

93

The preceding chapters discussed the given and required comfort conditions for the visual

environment as it relates to a school situation. This chapter addresses the product of the

bioclimatic equation and outlines strategies to achieve the required control.

R e q u ired C o n t r o l s

Control o f the external climate in the context of the visual environment is one of

exclusion. In order to create a suitable interior visual environment, the vast quantities of

light provided by the sun and the sky need to be tempered.

Sydney has an average horizontal illuminance level of 8500 lux, infinitely higher than the

320 lux maximum required illumination level. The need for control arises because most

buildings are constructed primarily of materials that are opaque to natural light. Light is

easily excluded from the inside of a building and when transparent openings are provided,

light is no longer distributed uniformly within the space. The fact that many apertures are

placed in a vertical position adds to the unevenness of light penetration.

Seasonal climatic changes, such as overly cloudy days will also affect the quantity and

quality of the available light.

Building O c c u p a n c y

Natural light is available only when the sun is in the sky. School classrooms are often

occupied from 7:00 a.m. to 10:00 p.m., so for at least part of the day, natural light will not

be available.

As indicated earlier, classrooms are used year round, apart from a six week summer

vacation that occurs from mid December through to the end of January and other shorter

holidays.

94

L ig h t in g A p p roaches

Two approaches exist for internal illumination. The first disregards all natural light and

only utilizes electric or artificial light. The second uses natural light when it is available and

when it is insufficient to meet the visual needs of the space, provides artificial light as a

secondary system.

The selected horizontal illumination level occurs for at least 90% of the working year,

therefore, for at least 10% of the year natural light will not be enough to provide the

required level of internal illumination. If illumination is required at night, electrical

lighting is the only available source.

E lectr ic l i g h t i n g

Electric lighting utilizes electricity as its source of energy. Electricity is forced through a

filament that becomes super hot and discharges energy as light and heat.

Electric lighting is flexible, versatile and, baring power blackouts, reliable. It is also the

biggest consumer of electricity in most buildings.

L ig h t Sou rces

An electrical lighting system is comprised of the lamp, the luminaire and the luminaire

layout. The lamp is the light source, the luminaire controls the distribution of light and the

layout influences the distribution of light throughout the space.

L a m p T y p e

The table below (Fig. 7.01) sets out the variety of lamps available and presents information

about each type. The criteria for selecting a lamp include efficacy, flexibility, lamp life,

cost and color rendition.

95

LampGroup

Incandescent Fluorescent Metal Halide High-pressureSodium

A dvantages Excellent optical Very good for Good optical Good opticalcontrol (e.g. very diffused, wide control controlnarrow beams of are, low Excellent color Very high efficacylight are possible) brightness rendition Very long lamp

Very good color rendition (especially the warm colors and skin tones)

Very low initial cost (especially useful when many low-wattage lamps are used)

Flexible (easily dimmed or replaced with another lamp of a different wattage)

lighting Good color rendition (varies greatly with lamp type)

Very good efficacy

Long lamp life

(especially of blue, green and yellow)

High efficacy Long lamp life

life

D isadvantages Very low efficacy Little optical 5 to 10 minute Color rendition is(high energy costs control possible delay in start or only fair (mostly

Very low lamp life (no beams) restart orange and(highmaintenancecosts)

Adds high heat load to buildings

Large and bulky (except new compact types)

Sensitive to temperature and therefore not used much outdoors

Fairly expensive yellow)About 5 minute delay in start and restart

Applications For spot, accent, For diffused even For diffused For diffusedhighlighting and lighting of a lighting or wide lighting andsparkle large area beams (offices, wide beams(residential, (offices, schools, stores, schools, where color isrestaurants, residential, industrial, not importantlounges,museums)

industrial) outdoors) (outdoor, industrial, interior and exterior floodlighting)

Efficacy(lum ens/W att)

10-25 40 -90 80-120 80 - 140

Life(hours)

750 - 2500 8 000 - 20 000 9 000 - 20 000 20 000 - 24 000

F igure 7 .01 : C o m p ariso n o f L am p T ypes

96

Efficacy is an indication of the amount of light a lamp will provide in relation to the

energy it consumes. Incandescent lamps have a very low efficacy, converting only 7% of

the energy they consume into light. Fluorescent lamps are more efficient, converting 22%

of electricity into light1. The release of heat accounts for the remaining electrical usage,

affecting the thermal conditions within the space.

Flexibility refers to the ease with which the lighting system can be altered. Dimming

systems are advantageous in a situation where lighting conditions may need to be changed

regularly. Fluorescent lamps are expensive to dim but can be set so that a form of

dimming can be achieved by separately controlling various tubes within the luminaire.

Start up time is also a consideration. Both metal halide and sodium vapor lamps require

substantial start up time, or time until they reach a suitable level of light production. This

can be particularly problematic in emergency situations so instant start up lamps are often

installed as a back up system.

Lamp life reflects the length o f time the lamp will be functional. This is an issue if lamp

replacement is difficult or if maintenance is irregular.

Cost usually refers to the initial cost of the lamp but can also refer to the life cost of

running it. The issue of cost is linked to lamp life as the more costly lamps usually have a

longer life and are therefore replaced less frequently.

Color rendition relates to the energy wave lengths that the lamp produces. No lamp

replicates daylight, although some come close to it. Most lamps have a concentration of a

particular color and this can result in inaccurate color recognition. Incandescent lamps tend

to be warm, producing increased yellow and red light, whilst fluorescent lamps tend to be

97

cooler, producing blue and green light. Color balanced, or corrected, fluorescent tubes can

come closest to transmitting daylight patterns of color.

Fluorescent lamps are usually chosen for general lighting in schools. They produce good

diffuse light over large areas and have a long lamp life, a high efficacy rating and good

color rendition. Most fluorescent luminaires group a number of tubes together and can be

designed so that individual tubes can be turned on and off independently, producing

inexpensive dimming.

L u m in a ir e s

The luminaire is the part of the system that holds the lamp and is responsible for

controlling the distribution of light. A luminaire is a combination of various materials

which, depending on their placement, will control the distribution of light. These materials

can be reflective, transparent, translucent or opaque.

The figure following (Fig. 7.02) indicates the six primary types of luminaire, based on the

percentage of light distributed in specific directions, namely upwards towards the ceiling,

or downwards towards the workplane.

The distribution of light from the luminaire will influence the overall effect of the lighting

scheme. The more light that is directed up onto the ceiling, the more diffuse the overall

effect.

Efficiency of light distribution relies on the choice o f luminaire and the reflectance of the

surfaces of the room. If all light is directed to the ceiling the only light available for task

performance is reflected and diffuse light, whereas if all light is directed downwards to the

work surface the ceiling is not utilized to enhance light distribution.

98

Symbol Type % of light upwards

% of light downwards

Explanation

A D ire c t 0-10 90 -100 Direct: direct lighting fixtures send most of the light down to the workplane. Since little light is absorbed by the ceiling or walls, this is an efficient way to achieve high illumination on the workplane.Direct glare and veiling reflections are often a problem, however. Also shadows on the task are a problem, when the fixture-to-fixture spacing is too large.

%Sem i-d irect

10-40 60-90 Semi-direct: Semi-direct fixtures are very similar to direct luminaires except that a small amount of light is sent up to reflect off the ceiling. Since this creates some diffused light as well as a brighter ceiling, both shadows and the apparent brightness of the fixtures are reduced. Veiling reflections can still be a problem, however.

' 1 x

G en era lD iffuse

40-60 40-60 General diffuse: This type of fixture distributes the light more or less equally in all directions. The horizontal component can cause severe direct glare unless the diffusing element is large and a low-wattage lamp is used.

D irect-ind irect

40-60 40-60 Direct-indirect: This luminaire distributes the light about equally up and down. Since there is little light in the horizontal direction, direct glare is not a severe problem. The large indirect component also minimizes shadows and veiling reflections.

%Semi-indirect

60-90 10-40 Semi-indirect: This fixture type reflects much of the light off the ceiling and thus yields high-quality lighting. The efficiency is reduced, however, especially if the ceiling and walls are not of a high reflectance white.

Indirect 90-100 0-10 Indirect: Almost all of the light is directed up to the ceiling in this fixture type. Therefore, ceiling and wall reflectance factors must be as high as possible. The very diffused lighting eliminates almost all direct glare, veiling reflections, and shadows. The resultant condition is often called ambient lighting.

Figur e 7 . 0 2 : C o m p a r i s o n o f L u m in a ire T y p e s

99

A direct-indirect or general diffuse system is most suited to a classroom application. It

allows light to be fairly equally distributed both upwards and downwards. Modeling of

objects is enhanced by shadowing, but the presence of the reflected component softens the

shadows so that they are not distracting. The use of diffusers and louvers in the base o f the

luminaire will prevent glare caused by exposed light sources.

L u m i n a i r e L a y o u t

The layout of luminaires within the room determines the distribution of light throughout

the space and is based on the light level requirements. Some layouts provide a uniform

level of light throughout the space, whilst others mirror the needs of specific tasks. A

layout should not produce a dull, uniform light level that resembles an overcast sky as this

can be psychologically disturbing to the occupants. However, it must also avoid creating

overly bright or overly dim areas, unless this contrast is desired.

L ig h t in g S tra te g ie s

Electric lighting design requires all the aforementioned issues to be resolved in such a way

that the resultant system provides the required light levels and desired light distribution.

Szokolay proposes the total flux concept for lighting system calculations, whereby the

quantity of flux installed (Oz) is greater than the flux received (Or) by a ratio referred to as

the utilization factor (UF).

This relationship allows the amount of lighting that needs to be installed to achieve a

desired flux level on the workplane to be determined. Utilization factors are usually

supplied by the manufacturers, as an indication of the effectiveness of their product. The

utilization factor is dependent on five factors: the properties of the luminaire, and whether

100

it is open or closed; the DLOR, which relates to the amount of light emitted upwards and

therefore partially absorbed by the ceiling and walls; the reflectance of the ceiling and

walls; the proportions of the room, which define the amount of light striking the walls in

relation to the percentage that directly reaches the workplane; and the direct ratio, which is

a measure of the percentage of the light emitted by the luminaire that directly reaches the

workplane2.

Various calculation methods can be used to determine the number o f lamps to satisfy the

lighting requirements. Due to the interconnected nature o f a lighting design system there

is no single solution to the many issues that need to be addressed and it is necessary to

define the requirements that the system must fulfill and prioritize the secondary issues.

The figure below (Fig. 7.03) tabulates these calculations for the basecase.

101

Lumen Method

length of room 11 mwidth of room 7.75 mArea 85.25 m2

Height of room 2.7 mH of workplane 0.7 mHm 2 m

R.I.= 1 x w 2.27(l+w)Hm

E 320 luxFlux rec. =A x E

27280 1m

Conversion factorsUF 0.43 recessed modular

diffuser (DLOR=50%)

MF 0.8

Flux initial =Flux rec./ UF x MF79302 1m

Lamp chosen 1.5m/65W4400 w output

68 Im/W0.75 conv for natural tube

3300 W revised output

Number of 24 requiredlamps

F igu re 7 .03 : L um en M eth o d ca lcu la tio n s

The glare index must then be calculated to reduce the probability of the luminaire

resulting in unacceptable glare situation. Calculations must fall within the limits set by

lighting standards. The figure below (Fig. 7.04) presents the calculations for the basecase.

Glare index

Assumptionsfloor is lightceiling 70%walls 50%luminaire BZ 3 tubular

4600 cm20% DLOR

54% ULOR3300 output

Height 2.7eye level 1.2H 1.5 m

Room sizes 11 m7 H

7.75 m5 H

Initial glareindex crosswise endwise

13.4 15.5

Corrections crosswise endwiseinitial 13.4 15.5reflectances 4 4luminous area -7 -7downward flux 1.8 1.8height -0.8 -0.8total 11.4 13.5

Allowable 19glare index

Figure 7 .0 4 : Glare I n d e x c a l c u la t io n s

103

The use of daylighting as a lighting system in classrooms has been controversial.

Historically, classrooms were almost exclusively daylit. During the 1960s, research was

conducted into the benefit or otherwise of windowless classrooms. The result was that,

“while windows (or windowlessness) seem to have no impact upon students’

academic performance, strong economic arguments favor windowless schools, and

some equally strong psychological arguments oppose them”3.

Daylight provides a dynamic light source, due to the changing nature of the color,

contrast and light levels it provides4.

Energy efficiency provides one of the strongest arguments in favor of daylighting schools.

The figure below (Fig. 7.05) indicates a breakdown of the energy usage in an average

school. Electric lighting comprises approximately half o f the electricity consumed, therefor

any reduction in the use of electric lighting will result in energy savings.

D ay lig h tin g

Other2 0 %

Heatingand

Cooling30%

ElectricLighting

5 0 %

Figur e 7 .0 5 : E n ergy U s a g e in s c h o o l s

104

The sun is the source of all daylight. It radiates a constant stream of energy towards the

earth, some of which arrives at the earth’s surface in wavelengths within the visible band.

Light from the sun can be divided into two forms: sunlight which is received directly from

the sun and daylight which is received from the sky vault via reflection.

Sunlight is problematic as a light source because of the constantly changing position of the

sun and the intensity of its illumination value. Daylight is therefore the light most utilized

in the lighting of buildings.

Sky conditions will affect the quantity and quality of available daylight. On days when the

sky is clear sunlight is the primary light source, with less light being received from the clear

blue sky vault. When conditions are cloudy or overcast, the entire sky vault acts as a

diffuser and daylight is the primary light source. Partly cloudy days are an amalgam of

these two conditions, giving rise to an extremely variable situation.

Three types of daylighting are received by a building: direct light, diffuse light and

reflected light. Direct light is light that comes from the sun or the sky, with no

interference. Diffuse light is light that has been scattered by interaction with moisture in

the form of clouds or other contaminants in the atmosphere. Reflected light is light that

has been reflected off another surface, be it the ground or other surrounding surfaces.

These distinct types of light interact with the building in different ways and can be

controlled using specific techniques. The figure below (Fig. 7.06) illustrates these daylight

types.

D a y lig h t in g Sources

105

Diffuse

Direct

Reflected

F ig u re 7 .0 6 : T y p es o f D a y lig h t

Calculation Methods

There are two approaches towards quantitatively examining daylighting. The first involves

using “luminous quantities” ̂whereby a set o f outdoor conditions is assumed from which

internal values can be calculated. The second involves using “relative values”6, often

referred to as the “daylight factor m ethod” involving the calculation o f the ratio of

illumination o f a point internally to that of a point externally. This ratio will not alter

regardless of the variation in external conditions.

There are numerous methods of calculating the quantity of light that will reach a given

point. Some o f these methods are mathematical, others are physical.

The total flux or lumen method is similar to the method used for electric lighting design.

It involves establishing an illuminance on the window surface (Eui) then multiplying this

value by the area of the window {Aw) to give the total lumens entering the window (Of).

106

This is then multiplied with reduction factors to compensate for the effect of maintenance,

the type of glazing used and any bars or mullions present, to achieve an effective flux value

(Of).

If this effective flux value is divided by the floor area (A), an average illumination value is

obtained. If the illumination value at a specific point is required then a further factor, the

Utilization Factor (UP), needs to be included. This incorporates correction values for the

size and proportion of the room, the reflectance of the ceiling and walls, the type of

fenestration being used and the position of the point itself. The accuracy of this method is

not high, with best results being achieved when it is used with toplighting systems, where

certain spacing-to-height ratios are not exceeded.

The split flux method is a more accurate method. It considers the three separate

components of daylight: the sky component (SC), which is the light received from the

portion of the sky visible from the window, the external reflected component (E R C ),

which is the light entering the window after being bounced off the ground or other

external surface and the internal reflected component (IRC) , which is that part of the light

which arrives at a point after having been reflected off internal surfaces.

This method is complex, but its results are accurate for both toplighting and sidelighting.

Each component is calculated independently using tools developed for the purpose, the

most widely utilized of these being the Building Research Station (BRS) protractors, which

are used in conjunction with scaled plans and sections of the building to calculate the sky

component and external reflected component.

107

The most important issues to address when designing a daylighting system are the

resultant penetration and distribution of light within the daylit space.

Robbins7 has categorized daylighting systems according to a series of proportional

relationships as a way of evaluating and comparing the characteristics o f different systems.

The initial category of relationships are spatial, whereby the impact o f daylighting on the

space of a building is considered in relation to the volume and size of the space.

The ratio of envelope to floor area:

a = e / f e = envelope area

f = floor area

D a y lig h t in g Systems

The ratio of volume to floor area:

6 = v / f v = volume

f = floor area

When considering the usual ratio outcome for a daylit building (Fig. 7.07) the issue of

initial cost becomes apparent. Increased surface area in a design usually translates to higher

construction costs8. Daylit buildings usually have higher ratios than non-daylit buildings,

but there is some overlap in the figures, designers should aim to place their buildings in

this range.

a bDaylighted 0.80 - 2.25 1 1 .0 -2 2 .0Nondaylighted 0.3 - 2.00 9.0 - 14.0

Figur e 7 .0 7 : P r o p o r t i o n a l r e la t io n s h ip ratios

108

The second category focuses on the lighting performance of specific apertures.

The third category are the spatial / aperture relationships that encompass the association

between the aperture and the space it is daylighting. These ratios will be examined in

conjunction with specific daylighting systems.

These relationships attempt to classify the penetration and distribution of light within the

space. Penetration o f light refers to the possible lux levels that could be expected to occur

at specific points within the room, and is defined “as the distance into the room that

daylight reaches along the task plane at a predetermined level of illuminance”9. Light

distribution is designated by the extent of its latitudinal or longitudinal spread.

Latitudinal spread is defined as “the distance along which a predetermined level of

illumination extends perpendicular to the plane of the aperture along the work plane”10.

Longitudinal spread relates to the “distribution of daylight along the length of the

aperture”11.

The results of these findings are usually displayed using sections and floor plans of the

space being studied.

The single most significant factor affecting daylighting results is the sky condition. An

overcast sky will produce deeper penetration but softer shadows, whereas a clear sky will

not provide as deep a penetration but the shadows are sharper and more defined. Glare is a

problem irrespective of sky condition because of the high contrast between the aperture

and surrounding surfaces.

When using a section chart, results are graphed as a curve indicating illuminance level

against distance from aperture. When reading these charts three components are

109

important: the slope of the curve, the presence of any knees in the curve and the rate of

change of slope in the curve. The general shape of a curve will not alter, except due to

differing sky conditions, irrespective of the absolute illuminance present. Knees in the

curve are used as an indicator of a significant change in slope, while the rate of change in

the slope is indicative of changes in the illumination levels.

Daylighting systems fall into two categories, sidelighting and toplighting. Both systems

have positive and negative characteristics, making them suitable for different applications.

110

Sidelighting occurs in two forms, windows or view apertures, and clerestories or non-view

apertures. Positive characteristics of a sidelighting scheme include the strong directionality

of the light provided and the ability o f the scheme to provide lighting on a two

dimensional horizontal surface12. The negative characteristics relate to the problems of

glare created by having a light source that can be in the field of vision o f the observer.

W in d ows

Two sets of proportional relationships govern both forms o f sidelighting; penetration ratios

and spread ratios. Penetration ratios include the space height to sill height ( / / ) ratio, and

the ceiling height to aperture height (V ) ratio. The spread ratio is the ratio o f aperture

length to aperture height (A f). These variables are graphically represented in the figure

below (Fig. 7.08).

S i d e l i g h t i n g

/ / = f / h

V = H /h

M = 1/h

F i g u r e 7 . 0 8 : R a t i o v a r i a b l e s - W i n d o w

111

The variables that can be adjusted include H, which is altered by adjusting the height of

the aperture sill, V which is altered by manipulating the height o f the top plate of the

aperture, and M which is affected by changes to the width o f the aperture.

Ching defines a window as,

“An opening in the wall o f a building for admitting light and air, usually fitted

with a frame in which are set operable sashes containing panes o f glass’’13.

The figure below (Fig 7.09) displays the classic light penetration achieved by a window

aperture. The light level is highest directly adjacent to the opening, dropping off sharply

towards the opposing wall. This variability o f lighting is the biggest counter indication to

the use o f windows as the only source for daylighting.

a: aperture facing sun, clear sky b: overcast sky, any orientation c: aperture opposite sun, clear sky

F ig u re 7 .0 9 : P e n e tra t io n curve - W in d o w

112

C le re s to r ie s

A clerestory is defined as,

“A portion of an interior rising above adjacent rooftops and having windows

adm itting daylight to the interior”14.

Robbins refers to windows as view apertures and clerestories as non-view apertures, set into

the wall o f a building. Clerestories are further defined as being “any window whose sill

height is greater than eye height”15, the top plate also has to be at or below ceiling height,

otherwise the aperture is considered a roof light.

W hen considering clerestories there is the additional ratio o f height o f the aperture to the

distance to the opposing wall (Q ). The figure below (Fig. 7.10) indicates the variables

used in the ratios.

/ / = f/h

V = H /h

M = 1/h

Q = Q / f

F i g u r e 7 . 1 0 : R a t i o v a r i a b l e s - C l e r e s t o r y

113

In comparison to windows, clerestories provide superior vertical surface illumination

because they avoid the problem of overshadowing by elements in front o f the surface being

lit. The resultant lighting curve is slightly different as well, with the point o f maximum

illumination occurring away from the wall surface adjacent to the aperture. The figure

below (Fig. 7.11) graphs the basic clerestory lighting pattern. By varying the Q ratio, the

point of maximum illumination can be positioned by the lighting designer.

a: overcast sky

F ig u re 7 .1 1 : P e n e tra t io n curve - C le re s to ry

114

T o p l i g h t i n g

Toplighting can take a number of forms, including horizontal apertures or skylights,

angled apertures, sawtooth and monitor systems.

The positive characteristics of toplighting schemes include the evenness of light penetration

and the size of the area that can be lit. The negative characteristic is the obvious inability of

a toplighting scheme to light buildings beyond a single story, the exception to this being

beam lighting systems.

Penetration and spread are used to describe the distribution pattern produced by

toplighting schemes in much the same way as for sidelighting schemes.

The proportional ratios, of ceiling height to aperture height { H ) and aperture length to

aperture height ( M ) apply to all toplighting schemes, with additional ratios applicable to

specific types of toplighting.

H = [ / h

M = 1/h

When designing toplighting schemes there is an assumption that sunlight is excluded, so

all light is provided by daylight, therefore there will be differences due to sky conditions.

H o r iz o n ta l A per tu re s

Horizontal apertures, or skylights, are apertures in the flat roof of a space. An additional

ratio applicable to this scheme is the ratio of height of the aperture above the floor to the

width of the aperture ( N) . In all horizontal aperture calculations the thickness of the roof

is assumed to be minimal. When this is not the case the aperture becomes a light well and

115

exhibits different distribution patterns. The ratio for this situation relates the depth of the

aperture to the height o f the aperture above the floor (O ). The fig below (Fig 7.12)

illustrates the ratio variables.

N = H/w

0 = H /O

F ig u re 7 .1 2 : R a tio v a ria b les - H o r iz o n ta l a p e r tu re

The standard pattern of a single skylight under an overcast sky, shows a peak maximum

illumination level directly below the opening with light levels falling off sharply to either

side. Factors affecting this pattern include the installation o f multiple skylights, which will

provide a more even level of illumination. Varying Af will affect the longitudinal spread of

light, whilst altering 7 / will result in a reduced maximum illumination level and a flattened

slope to the lighting level curve. Altering O has significant effects on both the maximum

illumination attained and the spread o f light within the space. The figure below (Fig. 7.13)

illustrates the basic curve for a single skylight.

116

a: clear sky b: overcast sky

F ig u re 7 .1 3 : P e n e tra t io n curve - H o r iz o n ta l a p e r tu re

The differences o f pattern displayed by a horizontal aperture under a clear sky concentrate

on the position of the point o f maximum illumination which will move depending on the

position o f the sun.

A n g led A p e r tu re s

Angled apertures are skylights set in an angled roof. The ratio o f the distance from the

floor to the midheight of the aperture to the width of the aperture { G ) and the ratio of

the distance from the opposing wall to the middepth of the aperture, to the distance from

the floor to the midheight of the aperture (Q ) are specific to this system. The figure below

(Fig. 7.14) indicates the relevant ratios.

G = G /w

Q = Q /G

117

F ig u re 7 .1 4 : R a tio v a riab les - A n g le d a p e r tu re

The most distinct feature of the penetration pattern for this scheme is that the light levels

either side o f the point of maximum illumination are not equal. This pattern can be used

to create two distinct areas within a space, with differing lighting characteristics. The

figure below (Fig. 7.15) illustrates this light pattern.

Differing sky conditions produce minimal variation in the lighting curves produced by this

system, although the point of maximum illumination may move with the position o f the

sun in clear sky conditions.

a: overcast sky

F i g u r e 7 . 1 5 : P e n e t r a t i o n c u r v e - A n g l e d a p e r t u r e

118

S a w to o th A p e r tu re s

Sawtooth apertures are usually vertical apertures located above the ceiling line, coupled

with an adjacent angled ceiling with light entering from one direction only. Variations

exist utilizing angled apertures and bi-directional apertures, the later being referred to as

butterfly roofs. The location o f this system above the ceiling line differentiates it from

clerestories.

Additional ratios for a sawtooth system are the ratio of the floor to ceiling height to the

length o f the sloped surface o f the aperture (5 ), and the ratio of the length o f the sloped

surface o f the aperture to the distance between the apertures ( W) . The figure below (Fig.

7.16) indicates the ratio variables.

S = S/f

w = s/w

< ■ ■ >

F i g u r e 7 . 1 6 : R a t i o v a r i a b l e s - S a w t o o t h s y s t e m

119

Sawtooth apertures are usually used in series, the pattern displayed by a single aperture is

different to that displayed by a series of three or more. A minimum of three apertures are

needed to establish what is considered the typical sawtooth lighting curve. The figure

below (Fig. 7.17) illustrates this basic curve for differing sky conditions and building

orientations.

Vertical apertures located above the ceiling line are exposed to different sky luminance

values than those located below the ceiling line and are more readily affected by

differences in sky conditions. Different sky conditions and different orientations will

therefore alter the pattern o f light penetration and distribution.

Varying the distance between the apertures ( W ) increases the difference between the

maximum and minimum values of illumination. If the angle o f the glazing is altered, the

pattern begins to resemble that o f a series of angled apertures. Butterfly roofs display

patterns closely resembling that of a monitor system.

a: clear sky, aperture facing sun b: overcast skyc: clear sky, aperture opposite sun

F i g u r e 7 . 1 7 : P e n e t r a t i o n c u r v e - S a w t o o t h s y s t e m

1 2 0

M o n ito r A p e r tu re s

The monitor system differs from the sawtooth system in that paired bilateral apertures are

provided, which by definition, open to opposing parts of the sky vault.

The same ratios apply to a monitor system as to a sawtooth system but with the

complication o f the additional aperture. The effect o f bilateral light access is most

pronounced when considered under clear sky conditions. The figure below (Fig. 7.18)

indicates the ratio variables applicable to a monitor system.

S = S /f

w = s/w

F ig u re 7 .1 8 : R a tio v a riab les - M o n ito r sy s tem

A series o f apertures are needed to establish a typical monitor pattern and differences are

apparent at the edges of the series. The standard monitor lighting curve displays points of

maximum illumination directly below the raised portion of the monitor. Illumination

levels are equal on either side of this point under overcast skies, and unequal under clear

121

skies due to the influence of the sun. The figure below (Fig 7.19) indicates the basic curve

for these two sky conditions.

a: clear sky, apertures facing and opposite sun b: overcast sky

F ig u re 7 .1 9 : P e n e tra t io n curves - M o n ito r sy s tem

If M is manipulated the maximum and minimum levels o f illumination can be altered

with the curve becoming flatter, and with clear sky conditions, the position o f maximum

illumination can be moved. Varying the H ratio shifts the points o f maximum illumination

and stretches out daylight distribution. Altering the 5 or W ratio has the most significant

impact on the position of the points o f maximum and minimum illumination. Orientation

affects which parts o f the sky the apertures are exposed to and therefore exerts

considerable influence on daylighting distribution.

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D a y l i g h t i n g S t r a t e g i e s

E xis t in g D a y l i g h t in g S y s te m s

The basecase has large windows located in the north and south facades which provide a

substantial quantity of daylight for the classrooms.

The ratios for the North windows are:

# = 2 1 4 3 /1 3 7 1 = 1.6:1

y = 2700/1371 = 2:1

M = 4570/1371 =3.3:1

These ratios will vary from the basic ratios in that the altered H value, due to the raised sill,

will drop the maximum illumination point slightly. The change in the V value will also

create a drop in maximum illumination, as will the reduction in the M value. This window

has a higher sill and a lower head and is not as wide as the standard one.

The resultant light penetration and distribution will be less than that apparent in the

standard curve but will follow a similar pattern with the point of maximum illumination

occurring adjacent to the wall and falling off as it enters the room.

The ratios for the South windows are:

# = 2 1 4 3 /1 2 0 0 = 1.8:1

1/= 2700/1200 =2.3:1

Af= 4570/1200 =5.3:1

These ratios show variations similar to those of the north facade windows, despite the

windows being significantly wider with a higher sill.

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The rooflights in the basecase are angled apertures. They run parallel to the slope of the

roof and therefore face both N orth and South. These apertures focus daylight into the

center o f the space and are advantageous in balancing out the light entering through the

windows.

The figure below (Fig. 7.20) plots the lighting curves for the basecase. One curve has been

charted using points in the center o f the space, the other shows the lighting curve against

the west wall.

770 0Springing Height

200 lux

a: lighting curve along center line b: lighting curve along w est wall

F ig u re 7 .2 0 : L ig h tin g cu rves - B asecase (w ith w in d o w s)

The photograph below (Fig. 7.21) provides an indication o f the light distribution within

the space. Light is obviously concentrated at the windows, although the light level is

relatively uniform throughout the space.

124

F ig u re 7 .2 1 : P h o to g ra p h o f Base case (w ith w in d o w s)

2700 mmSpringing Height

200 lux

a: lighting curve along center line b: lighting curve along w est wall

F ig u re 7 .2 2 : L ig h tin g curves - B asecase (w ith o u t w in d o w s)

The basecase rooflights are not particularly effective on their own. W hen simulations

were run w ithout the windows, the resultant light curves where significantly flatter,

with the point of maximum illumination occurring in the center o f the room, the point

where the light from opposing skylights will merge. The figure above (Fig. 7.22)

displays these findings.

125

The photographs in the following figures (Fig. 7.23, 7.24) show the basecase without

windows. The truncation o f the rooflights is clearly visible in the second o f these images

(Fig. 7.24).

F i gu r e 7 . 23 : P h o t o g r a p h o f Basecase ( w i t h o u t w i n d o w s )

F i gu r e 7 . 24 : P h o t o g r a p h o f Basecase ( w i t h o u t w i n d o w s )

126

P ro p o se d D a y lig h tin g S ys tem s

The base case as designed has extensive sidelighting systems in place. The toplighting

system is minimal and does not fully utilize the potential of a single story building for

daylight penetration, so a series o f toplighting strategies were investigated.

In v e s tig a tio n P ro ced u re

The investigation o f possible daylight strategies was undertaken using a combination of

photometric and photographic methods, utilizing a “mirror-box” artificial sky, to provide

an accurate and consistent light source that can closely match a designated sky type.

The “mirror-box” type artificial sky is a rectangular light tight box with interior walls clad

with mirrors, the ceiling is composed of fluorescent lamps and a diffuser panel to provide

diffuse light. The multiple inter-reflectance generated by the mirrors created a simulation

of an overcast diffuse sky, with a luminance distribution similar to that of the CIE overcast

sky.

To produce useable results the variables within the scale model that effect light penetration

and distribution need to be accurately rendered. Interior surfaces need to be of a

reflectance similar to that of the actual space and apertures need to be sized and placed

correctly. Depending on the type of research being conducted, interior fixtures and

furnishings can be included but are not essential to overall general readings.

When a scale model is placed in the “mirror-box”, photometric and photographic results

can be generated for analysis.

127

P h o to m e tr ic A nalysis

The design of daylighting systems requires an analysis of both the quantity and quality of

the light that penetrates into, and is distributed within, the space.

Photometric analysis provides information related to the quantity of light available at

specific points within the space. Light sensors are used to measure the light levels achieved

by the various systems being studied. The figure below (Fig. 7.25) indicates the location of

the sensors within the study model.

F igure 7 .25 : L o ca tio n o f lig h t sensors

From these sensor readings graphs can be generated that indicate the distribution of light

within the space and the variation in light levels across the space. The quantity of light can

be measured as an illuminance level or as a factor of available exterior daylight.

P h o to g rap h ic A nalysis

The quality of light within a space is as important as the quantity of light. The way in

which light interacts with the physical design elements of the room will influence the

success of a daylighting system.

128

Photographic analysis involves photographing the interior o f the scale model in such a way

that the space can be conceived o f as if it was being viewed at full scale. The photographs

reproduced in this paper were taken using a 28mm lens, set so that eye level was consistent

with the scale model. These images graphically indicate the nature o f the light within the

test space.

S a w t o o t h S y s t e m

The first system to be examined was a sawtooth layout, utilizing a series o f four rooflights

equally spaced across the depth o f the room, with the glazed areas oriented north. The

figure below (Fig. 7.26) indicates the ratio variables for this strategy.

h2700 mm4

Fi gu r e 7 . 26 : Ra t i o var iables - S a w t o o t h

The spatial ratios are as follows:

H = 4400/1000 = 4.4:1

M = = oo:l

S = 2700/3700 = 0.7:1

W= 2500/0

129

The figure below (Fig. 7.27) indicate the resultant curves generated by this system, when it

was simulated with the sidelight windows. The additional light is most obviously of

advantage against the north wall.

3200 lux

a: lighting curve along center line b: lighting curve along w est wall

Fi gu r e 7 . 27: L i g h t i n g curves - S a w t o o t h ( wi th w i n d o w s )

The lighting values for the sawtooth system alone are presented in the figure below (Fig.

7.28) this demonstrates the classic increase in lighting levels under successive apertures.

200 lux

a: lighting curve along center line b: lighting curve along w est wall

Fi g u r e 7 . 28: L i g h t i n g curves - S a w t o o t h ( w i t h o u t w i n d o w s )

The photographs below (Fig. 7.29, 7.30) demonstrate the advantages and disadvantages of

this system. Light is fairly uniformly distributed within the space and the ceiling is well

illuminated. The apertures have been continued to the external walls and therefore these

walls are receiving high levels of light, although there is some shadowing related to the

130

rhythm of the apertures. The north wall is also markedly darker (Fig. 7.29) despite the

presence of windows.

F i gu r e 7 . 29 : P h o t o g r a p h o f S a w t o o t h s t r a t e g y

F i gu r e 7 . 30 : P h o t o g r a p h o f S a w t o o t h s t r a t e g y

One of the problems associated with this system is glare, as evidenced in the

photographs, where very large, very bright areas are within the viewers field o f vision.

This situation can be tempered by using tinted glazing materials or other shading

131

apparatus. These measures would need to be installed in order to facilitate the “brown ou t”

of the classroom for audio visual displays.

M onitor System

This strategy consisted of four monitors that were evenly spaced across the depth of the

room. The glazed apertures were oriented to face north and south. The findings indicate

the results achieved by an overcast sky simulation, so orientation was less o f a factor than it

would be in a clear sky situation. The figure below (Fig. 31) indicates the ratio variables for

this strategy.

1500mm k H1200 mm

Fi gu r e 7 . 31: Ra t i o var i ables - M o n i t o r

ratios used were:

H = 4150/1000 = 4.1 :1

M = = °o : 1

5 = 4150/1500 = 2 . 8 : 1

W = 1500/1200 = 1.2:1

132

The figure below (Fig. 7.32) graphs the results obtained for this monitor system, in

conjunction with the windows. The light curves display the more uniformity o f light levels

obtainable with this type of system. The monitors in this case have a small 5 ratio and this

increases the light level as a higher proportion o f glazing is included over a given floor area.

200 lux

a: lighting curve along center line b: lighting curve along west wall

F ig u r e 7 . 32: L i g h t i n g curves - M o n i t o r (wi th w i n d o w s )

W hen this system was simulated without the windows, the results showed a distinct point

of maximum illumination. The figure below (Fig. 7.33) graphs these results.

a: lighting curve along center line b: lighting curve along west wall

Fi gu r e 7 . 33: L i g h t i n g curves - M o n i t o r ( w i t h o u t w i n d o w s )

133

The photographs below (Fig. 7.34, 7.35) indicate the uniformity o f light distribution

within the space and the equivalent light levels of the walls, some shadowing is seen on the

walls perpendicular to the monitors. There is also evidence of glare, although measures

similar to those outlined for the sawtooth system would greatly alleviate these problems.

F i gu r e 7 . 34 : P h o t o g r a p h o f M o n i t o r s t r a t e g y

F i gu r e 7 . 35: P h o t o g r a p h o f M o n i t o r s t r a t e g y

E n d n o te s

1 Lechner, p283.2 Szokolay, p i56.3 Robbins, plO.4 Robbins, p4.5 Szokolay, pl03.6 Szokolay, pl03.7 Robbins8 Robbins, p65.9 Robbins, p66.10 Robbins, p66.11 Robbins, p66.12 Robbins, p66.13 Ching, p271.14 Ching, p274.15 Robbins, p80.

Thermal Strategies

Table of Contents

Required Controls 138

Building Occupancy 140

Building Thermal Balance 141

Active Thermal Controls 142

Design Temperatures 142

Required Heating Capacity 143

Required Cooling Capacity 144

Active Strategies 145

Passive Thermal Controls 147

Passive Solar 150

Mass Effect 157

Air Movement 160

Endnotes 165

136

Table of Figures

Figure 8.01: BuildingBioclimatic Chart 138

Figure 8.02: Indication o f M onthly Thermal Comfort 139

Figure 8.03: H V A C Elements 145

Figure 8.04: Building Bioclimatic Chart (with Control zones) 148

Figure 8.05: M onthly Strategy Recommendations 149

Figure 8.06: Solar Path fo r Sydney, Australia. 154

Figure 8.07: M onthly overheated period 155

Figure 8.08: Solar path indicating overheated period 1 5 6

137

Preceding chapters have presented information pertaining to the two primary variables in

the bioclimatic equation. This chapter will resolve this equation as it relates to the thermal

environment; identify the conditions that require control and present strategies that can

accomplish this.

R eq u ired C o n t r o l s

In order to identify climatic conditions requiring control a Building Bioclimatic Chart was

created for the climate being considered. The chart below (Fig. 8.01) plots the monthly

climatic conditions as a series of lines, with the comfort zone as indicated.

(see Appendix E)

30

!0 25 £Dry Bulb Temp: deg C.

15

0 Thermal Comfort Zone

Figure 8 .01: B u ild ing B io c lim atic C h a r t1

138

le H

umid

ity:

g / k

<

Analysis of this chart indicates that although Sydney experiences a temperate climate, for

at least some part of the day, during all months of the year, conditions are such that they

occur outside the thermal comfort zone. During the summer months o f December,

January and February, the maximum conditions experienced are above the upper limit of

the comfort zone, whilst the minimum conditions are at the lower end of the zone. During

the winter months of June, July and August, both maximum and minimum conditions are

below those of the comfort zone. The figure below (Fig. 8.02) tabulates the monthly

conditions in relation to the need for heating and cooling. Overall, heating is the most

important thermal requirement.

M onth Max. Temp Min. Temp

Strategy Required: Strategy Required:

January Cooling Comfortable

February Cooling Comfortable

March Cooling Heating

A p ril Cooling Heating

M ay Comfortable Heating

June Heating Heating

July Heating Heating

August Heating Heating

Septem ber Comfortable Heating

October Comfortable Heating

N ovem ber Cooling Heating

Decem ber Cooling Heating

F igure 8 .02: In d ic a tio n o f M o n th ly T h e rm a l C o m fo rt

139

These charts are generated from monthly mean climatic data and not from the extremes

that can occur, which by definition would be further removed from the zone of thermal

comfort.

B u i l d i n g Occupancy

The range of temperature and humidity plotted on the Building Bioclimatic Chart gives

an accurate indication of the climatic conditions, but other variables need to be considered

in order to form a comprehensive overview of the climate as it relates to a specific building.

These variables relate to the occupancy of the building, when the building is occupied, and

who the occupants are.

School classrooms are usually occupied by a teacher and students between the hours of

8:00 a.m. and 4:00 p.m. Before class the teacher may be the only occupant and after class

some classrooms may be used for after-school care, community classes or meetings.

Therefore, the room might be occupied from 7:00 a.m. till 10:00 p.m., but rarely

overnight.

Thermal comfort need only be achieved within the classroom space whist it is occupied. A

cooling down of the room overnight is not a problem as long as it can be warmed up in

time for the beginning of the school day.

Occupancy of school classrooms is not consistent throughout the year. In New South

Wales schools close for a summer recess from the middle of December until the end of

January. Other two week breaks occur throughout the remainder o f the year but these have

little effect on the thermal control of the building as they are not of a long enough

duration.

140

Having determined what controls are necessary throughout the year it is now possible to

look at the methods available to provide them. Controls can be divided into two primary

types: active controls, utilizing Heating, Ventilation, Air Conditioning (HVAC) systems,

and passive controls, utilizing non mechanical systems. This paper concentrates on the use

of passive systems, but will provide a brief overview of active controls will be presented.

B u i l d i n g T h e r m a l B a la n c e

To determine the thermal balance of a building three primary heat flow rates must be

calculated: heat gain or loss, the cooling or heating load and the heat extraction or

addition rate2.

Heat gain is “the rate at which heat enters or is generated within a space at a given

instant”3, and can be “classified by the manner in which it enters the space”4, such as:

• “Solar radiation through fenestration.

• Heat conduction through the envelope.

• Heat generated within the space by people, lights, electrical equipment or

appliances, or any other electrical, mechanical , or thermal processes within the

space.

• The exchange of cool indoor air for warmer outside air by infiltration and/or

ventilation.”5

Heat loss is “the rate at which heat flows out of a space to the surrounding environment”6.

This flow can be classified as:

• “Heat conduction through the envelope.

• The exchange of warm indoor air for cold outside air by infiltration or

ventilation.”7

141

A c t iv e Therm al C o n t r o l s

Active thermal controls involve the mechanical addition or subtraction of heat from a

space in order to offset heat gains and losses and maintain interior conditions at a

comfortable level.

D e s ig n Temperatures

Prior to embarking upon heating and cooling load calculations it is necessary to determine

certain parameters. Design temperatures must be determined for both indoor and outdoor

conditions. The indoor design temperature is set by the thermal comfort zone, whilst the

outdoor design temperatures are set by climatic conditions.

The winter indoor design temperature was selected at 22°C, whilst the outdoor design

temperature was selected at 5.6°C, representing the lowest temperature experienced for

97.5% of the time during the months of June, July and August.

The summer indoor design temperature was set at 23°C, and is at the lower end of the

comfortable range due to the nature of the occupancy of the space (i.e. approximately 30

active children in each class). The outdoor design temperature is based on peak summer

conditions and represents “the hottest temperature, the highest likely coincident solar heat

gain, maximum occupancy, and the highest simultaneous equipment on line”8. The

temperature selected was 28.9°C and is the 2.5% Design Dry Bulb (DDE), so only 75

hours of this three month period will exceed this situation.

142

R e q u i r e d H e a t i n g C a p a c i t y

Calculation of a heating load provides a figure that represents the amount of energy that

will need to be added to a building to offset the heat losses. The components of a building

heat load include:

• “Transmission heat loss through:-

• Fenestration.

• Opaque walls.

• The roof.

• The floor, below grade walls, slab edge, etc.

• Outside air heat losses:-

• Due to infiltration and/or ventilation.”9

When calculating the heating load all the above factors need to be considered.

Transmission heat loss is calculated for all exterior surfaces using the formula:

Load = net area x U-factor x AT

Outside air load is calculated using the formula:

Load = L/s x O.A. factor x AT

Total heat loss is the addition of all these calculations, (see Appendix F)

Heat loss for the basecase was calculated at 377.5 kW. This is a peak heating load and

indicates the maximum heating that will be required in the building during the year. This

figure can be translated to a rate of fuel consumption if additional factors such as year

round climatic conditions and fuel efficiency are considered.

143

R e q u i r e d C o o l in g C a p a c i t y

The procedure for calculating cooling loads is similar to that for heating loads, but is more

complex. The peak cooling load condition does not correlate to the incident of highest

heat gain because some of the gain is absorbed by materials present in the space and will

not be released until a later time. The components of a building cooling load include:

• “Solar heat through fenestration.

• Transmission heat gain through:-

• Fenestration.

• Opaque walls.

• The roof.

• Internal heat gain from:-

• People.

• Lights.

• Electrical appliances and equipment.

• Outside air heat gain:-

• Due to the exchange of cool indoor air for hot outside air by

infiltration and/or ventilation.”10

In calculating cooling loads, both latent and sensible heat gains are considered.

Solar gains are calculated using heat gain factors and shading coefficients.

Transmission gain is calculated using the formula:

Load = net area x U-factor x AT

Internal heat gain is calculated from a survey of occupants and equipment.

144

Heat gain from outside air is determined by the formula:

Load = L/s X O.A. factor x AT

Total cooling load is an addition of these calculations, (see Appendix F)

The cooling load for the basecase was calculated at 463.$ kW. This is a peak cooling load

and indicates the maximum cooling that will be required in the building during the year.

As with the heating load, this figure can be translated into a rate o f fuel consumption when

additional factors such as year round climatic conditions and fuel efficiency are

considered.

A c t i v e S tr a te g i e s

In choosing an HVAC system the basic elements must first be decided upon. These

include:

• “Equipment to generate heat or cooling.

• A means of distributing heat, cooling, and/or filtered ventilation air where

needed.

• Devices that deliver the heat, cooling, and/or fresh air into the space.”11

The diagram below indicates these HVAC elements (Fig. 8.03).

HEATING and COOLING SOURCESDISTRIBUTION SYSTEMS

FurnaceBoilerHot Water ConverterIncineratorSolar EnergyD-X Air ConditionerElectric Water ChillerAbaorption Water ChillerEvaporation Cooler

DELIVERY SYSTEMS

Fin Tube Radiation Unit Heater Radiant Heater Fan Coil Unit Unit Ventillator PTAC Unit Air Outlet

Fi gu r e 8.03: H V A C E l e m e n t s 12

145

A series of interconnected issues will determine which system is selected. These issues

include: initial and life cycle costs; suitability for the intended occupancy; floor space

required for equipment; maintenance requirements and equipment reliability, and

simplicity of controls13.

146

Pass ive T herm al C o n t r o l s

Passive control systems do not rely on mechanical equipment but rather utilize the fabric

of the building itself and its surroundings to control and enhance the thermal environment

within the building.

The building is looked upon as a “combined solar collector and storage unit”14. It can be

conceived as being composed of the following elements: solar collectors or glazed

apertures that are exposed to the sun; a means of storing the heat that is collected; and an

insulated outer skin to restrict the flow of energy15. Depending on the control required,

different permutations of these elements will produce the desired effect.

In order to evaluate the strategies presented, computer simulation was performed using the

Calpas16 program. A basecase was developed that represented the home base block as it is

currently designed, and then each strategy was simulated independently to observe its

impact upon energy usage. The results have been used to compare the effectiveness of one

strategy in relation to another, rather than for quantitative calculation of energy usage.

A preliminary analysis of the Building Bioclimatic Chart provided an initial indication of

the controls that would be required to provide thermal comfort within a building located

in Sydney. A more detailed analysis can be undertaken if the Building Bioclimatic Chart is

enhanced with the inclusion of potential control zones. These zones, shown on the chart

below (Fig 8.04) indicate the passive strategies that will be most effective in combating the

extremes of climate that occur. From this chart it is possible to deduce for each month a

set of strategies that can passively counter the existing climatic conditions. A tabulated

form of these findings is presented below (Fig. 8.05).

147

Requirements for passive heating occur for a substantial part o f the year. The period from

May to October experiences under heating for at least part o f the day, with conditions

dropping into the solar input and winter mass effect control zones. Passive cooling is also

required during the year, with the period from October to April experiencing overheating

for part o f the day. During these months conditions rise into the summer mass effect and

increased ventilation control zones.

Q Thermal Comfort Zone

Passive Solar Gain

20 2 5 30Dry Bulb Temp: deg C.

Air Movement Effect

Fi gu r e 8 .04: Bu i l d i ng B i o c l i ma t i c C h a r t (wi th C o n t r o l zones)

148

g / k

<

Therm al Solar InputStrategy Indicated

HeatingMax. Temps

Mass Effect ThermalIndicated Com fortHeating

MayJuneJulyAug.

Sept.Oct.

Mass EffectIndicatedCooling

Jan.Feb.Mar.April

Nov.Dec.

Min. Temps

MayJuneJulyAug.Sept.Oct.

Jan. JanFeb. Feb.Mar. Mar.April

Nov.Dec.

F igure 8 .05: M o n th ly S tra teg y R eco m m en d a tio n s

VentilationIndicatedCooling

Jan.Feb.

Dec.

149

Passive Solar

Passive methods of heating a space utilize the solar energy of the sun. This energy is

allowed to penetrate the building envelope and heat the interior. Strategies fall into three

distinct forms: direct gain, thermal storage walls and sunspaces17. The primary differences

in these systems lie in the relationship between the aperture and the mass associated with

it.

Passive solar systems require some combination of the following elements;

• equatorial facing glazed apertures

• mass material for energy storage.

W ithin these elements there exists endless variations but the basic concept does not

change. An aperture is required to allow solar energy to penetrate into the building. This

aperture is usually glazed so as to take advantage of the imperviousness of glass to short

wave radiation. Solar energy, which is long wave radiation, is transmitted through the

glass. It interacts with materials within the space and is re-radiated as short wave radiation

which cannot exit through the glass, so is effectively trapped within the building, providing

heat. Mass acts as a collector, by absorbing some of this heat and storing it until the laws of

thermodynamics dictate that the reverse will occur, whereupon the mass radiates the heat

into the space. The inclusion of mass in passive solar systems serves to even out solar gain.

Direct gain systems rely on solar energy directly entering the space and warming it. Mass

is not an integral part of this system, although it does enhance its efficiency. Variations to

this system involve a choice of glazing, size and orientation of apertures, and shading and

insulation of the glass.

150

Thermal storage wall systems require mass to be located directly adjacent to the glazing.

Solar energy passes through the glass and strikes the mass, which absorbs the heat. The

heat delivery to the space is therefore delayed. The apertures used in this system cannot

function as view apertures, because of the adjacent mass blocking it. This system is not

efficient at providing heating during the day, so is often combined with a direct gain

system.

The last type of passive solar systems are sunspaces. These developed from the concept of

greenhouses and are an extension of the thermal storage wall system. In this system the

mass wall is pulled away from the glazed aperture resulting in the formation of a room.

Variations in this system arise from the way in which the sunspace is connected to the

space and the way heat is transferred from the sunspace to the space.

Passive solar systems rely on maximizing solar energy collection. Strategies to improve

their efficiency include, maximizing equatorial facing windows (north windows in the

Southern Hemisphere), installing roof lights and shaping and orienting the building as a

whole so as to increase its exposure to the winter sun. Other strategies to increase the

amount of solar energy entering the space include, enhancing the reflectance of

surrounding ground surfaces and using reflectors to bounce heat into the space.

These systems have an inherent problem because of the low insulation value of glass. While

glazed apertures allow solar energy to enter the building during the day, at night they are

the biggest source of heat loss through the envelope of the building. Strategies to offset

this problem include minimizing glazing in all the walls that do not receive constant winter

sun, namely the east, south and west walls. Apertures in these walls do not receive enough

sun during the day to counter the loss of heat at night. Another strategy is to utilize some

151

method of insulating the glass. This can take numerous forms but basically involves using

another material to cover the glazing at night to allay heat loss.

In choosing strategies suitable for improving the basecase consideration was given to its

current design and its intended function.

The basecase currently has large amounts of glazing on the north facade so increasing this

area was not practical. The option of incorporating roof lights was addressed in relation to

the provision of daylighting. The orientation of the basecase is hypothetical and currently

the long elevation of the building faces north, which is ideal. Therefore the strategy that

was investigated concentrated on increasing the solar heat being bounced into the building

by increasing the reflectance of surrounding ground surfaces. Changes were not significant

with only a 5% drop in heating load. However, the cooling load was significantly

increased, illustrating that in trying to solve one issue another can be exacerbated..

Strategies designed to reduce heat loss through glazing were more effective. The removal

of south facing windows dramatically reduced both heating (12%) and cooling loads (1.

However, such a dramatic design change would seriously compromise daylighting and

psychological comfort within the classrooms. The simulated installation of night insulation

was effective at reducing cooling loads but had no effect on heating loads.

Passive solar input is primarily a heating strategy and when climatic conditions cause

overheating of the space, the heat intake must be controlled by blocking or reflecting solar

access to both the opaque and transparent components of the external envelope. The walls

will transmit heat to the interior at a rate which is dependent on the material and the

presence or absence of insulation materials. The windows provide the biggest source of

152

solar energy input. This can be used to advantage when heating is required, but is

deleterious when cooling needs are paramount.

Shading is the most commonly utilized cooling strategy and needs to be provided for all

solar gain windows and can be used for walls as well. The design of shading for windows

depends on the solar path, the times that solar input is undesirable and the window size

and orientation.

The graph below shows the solar path for Sydney (Fig. 8.06). From this diagram it is

possible to calculate the position o f the sun in relation to both azimuth and altitude, at any

time of the day, for a representational day of each month of the year.

In order to calculate when solar input is undesirable the hourly temperatures are tabulated

for a representational day for each month of the year (Fig. 8.07). Any time of the day

during which the temperature rises above 21°C, overheating can occur. When these times

are transposed onto the solar path an area corresponding to the times that it would be

desirable to exclude solar input from the building is shown (Fig. 8.08). Design of a

shading device involves devising a combination of vertical and horizontal fins in a

configuration that allows solar energy to enter the apertures when heating is required, but

be blocked when overheating is likely to occur.

153

True NAdjusted N

,15May

21 Mar E

150ct

/ 6VT8 \

13Nov

22Dec

F igure 8 .06: Solar P a th fo r S yd n ey , A u stra lia

154

M onth

January

February

March

A pril

M ay

June

July

August

Septem ber

October

Novem ber

Decem ber

From:

9:00 am

9:00 am

9:30 am

11:00 am

N /A

N /A

N /A

N /A

N /A

11:30 am

10:15 am

9:30 am

To:

10:00 pm

10:00 pm

7:45 pm

5:45 pm

N /A

N /A

N /A

N /A

N /A

5:00 pm

6:15 pm

7:45 pm

F igure 8 .07: M o n th ly o v erh ea ted p e rio d

True NA djusted N

1 5 0 c t

I 6Vr18 \

13Nov

22D ec

Summer overheating period

Spring / Fall overheating period

F igure 8 .08: Solar p a th in d ic a tin g overh eated perio d

156

Mass Effect

Another issue related to passive solar heating systems involves the provision of mass.

Thermal storage walls and sunspaces rely on the provision of mass in order to perform

their functions. Direct gain systems function more efficiently when mass is present,

although it is not an integral part of the system.

Mass functions as both a heat storage material and as a buffer between the outside and

inside environments. High capacitance materials are used as mass because they have an

ability to readily absorb heat, materials such as concrete, brick and earth fall into this

category.

Massive materials need to be exposed to the space in order to act as a heat sink or storage.

Solar energy entering the space will heat the air and any mass material it strikes. Material

not directly exposed to sunlight will be heated indirectly as the colder material absorbs

energy from the warmer air. The mass does not relinquish this stored heat until the air

temperature drops to a point where it is cooler than the material. This delay of heat release

is useful in flattening out day to night variations in the temperature experienced within the

space.

Massive materials in external walls can act as a buffer between the external and internal

environments. The same processes that make massive materials useful for heat storage can

also be utilized to delay heat transfer from the outside to the inside of the building. This

delay is referred to as time lag its length is dependent on the material itself and its

thickness. Solar energy striking the external skin of the material slowly heats it up and this

heat is then transmitted through the material to the inside surface via conduction. The

time lag for this can be as much as ten or twelve hours, therefore heat will be entering the

building when the space is no longer receiving solar input and is beginning to cool down.

157

The use of mass as a cooling strategy relies on the same principles. Mass located with a

direct connection to the internal space will absorb heat present in the space, negating the

need for it to be cooled by alternative means. Mass located in the external walls will delay

the transmission of heat from the outside to the inside space. The use of mass does not

exclude heat from the space but rather, delays its release, providing an advantage in a

temperate climate where nights can be cooler. In a school the lag in heat transmission

during hot days is ideal, as the room will be unoccupied when the energy is radiated into

the space.

The basecase as currently designed contains no mass. The concrete floor, often used as a

convenient heat sink, is thermally insulated by carpet and vinyl tiles laid over it. The

external walls of brick veneer play a slight role in providing time lag delay of heat

transmission, but do not function as a heat sink material. No other mass materials are used

in the construction.

The strategies simulated related primarily to the choice of materials for major external

surfaces. These were limited to conventional materials that could easily be incorporated

into the existing design.

Slab on ground concrete slabs function well thermally as heat sinks, so strategies were

concentrated on the covering materials. When the basecase was simulated with an exposed

slab there was a significant decrease in heating and cooling loads of about 35% each,

indicating the benefit of providing thermal mass. Exposed concrete slabs are not a viable

option though for a classroom space. Other options that were simulated included a tiled

floor, which showed an improvement of about 35% in both heating and cooling, because

tiles are thermally conductive and act as mass. A combination of carpet in the classrooms

and tiles in the practical activities areas was simulated but showed little significant savings

158

in cooling and a significant increase in heating loads, due to the small percentage of tile in

relation to the area o f carpet. Some compromise between tiling and carpeting would seem

the most appropriate solution, ideally most of the classroom space would be tiled, with

carpet used in areas where the children are likely to be using the floor.

Wall materials are more easily manipulated. Currently the basecase external walls are brick

veneer consisting of a brick outer skin and a timber or steel framed inner skin. The

strategies simulated concentrated on increasing the mass effect o f these walls. One strategy

reversed the brick veneer, thereby relocating the brick skin to the inside and the timber

framed skin to the outside, putting the massive material in contact with the interior. The

framed layer also serves to insulate the mass from the outside temperatures so that heat is

not radiated externally or absorbed. This strategy resulted in significant cooling load

reductions of about 30%. Heating loads were also reduced by approximately 20%.

The second strategy that was simulated was a double brick construction, separated by an

air cavity. This system exposes the mass material to both the internal and external

environments. The results showed an increase in cooling load when compared to the

previous strategy due to the loss of the mass insulation, but heating loads maintained a

20% reduction.

Two other strategies involved replacement of the exterior brick skin with skins of different

materials. When concrete block was simulated it resulted in an increased heating and

cooling load. Hebei block was more successful with a 10% reduction in cooling load and a

15% reduction in heating load. Hebei block is an autoclaved aerated concrete block which

provided substantially more insulation value than brick, so this wall configuration is super

insulated rather than thermally massive.

159

A single strategy simulated in relation to the roof material involved replacing the existing

metal roof deck with a tile roof. This increased the cooling load by 5% whilst having

almost no impact on the heating load. This is believed to be due to the difference in

reflectivity between a light colored metal deck and a dark terra-cotta colored tile.

A i r M o v e m e n t

Ventilation is the introduction of outside air into an enclosed space or the movement of air

within the space. The introduction of outside air is essential in order to maintain the

quality of the air inside the building. Air quality is a health issue and relates to the supply

of oxygen, the removal of exhaled carbon dioxide and other contaminants and the

dilution of odors. The effect of outside air on the thermal balance o f the interior is

dependent on the quantity of air and the relative difference in internal and external

temperature and humidity levels.

Rates of ventilation are specified by legislation and are set at a level whereby a sufficient

quantity of fresh air is constantly being brought into the space to replenish the internal air.

Three issues arise in relation to air quality: oxygen supply, contaminant removal and odor

dissipation. The supply of oxygen is fundamental as it is the gas that humans extract from

the air when they breathe and is necessary for human life. Human exhalation produces

various byproducts, the primary one being carbon dioxide which in large quantities is

lethal to humans. Materials used in all forms of construction also produce byproducts that

are dangerous at high levels of concentration. These contaminants therefore need to be

removed from the air supply. Humans also produce odors from biological processes such

as sweating, which need to be diluted.

The thermal balance of the building can be greatly affected by ventilation, depending on

the variation existing between indoor and outdoor climates. When this variation is

160

extreme, incoming air needs to be conditioned. Energy that has been spent on

conditioning air that is being expelled will be lost. Infiltration, which will be explained in

detail later, is particularly problematic in this respect as its uncontrolled rates of exchange

increase as temperatures become more divergent.

Ventilation occurs in three forms, all of which can be present in a single space, forced

ventilation, natural ventilation and infiltration19.

Forced ventilation involves the mechanical movement of air and allows the highest level of

control over the quality and quantity of air that is introduced and circulated around the

building. This form of air handling is often mandatory in buildings where large quantities

of outside air need to be introduced to maintain internal air quality. Forced ventilation is

related to the use o f a HVAC system and is beyond the scope of this report.

Natural ventilation involves the movement of air through openings designed in the

building’s envelope. It is powered by wind and variations in temperature. The flow of air

within the building depends on the size and location of inlets and outlets and the layout of

partitions within the space.

Natural ventilation is used primarily as a cooling strategy. Ventilation can have a cooling

effect within a space through two processes, comfort ventilation and convective ventilation.

Comfort ventilation uses air moving across the skin to directly cool the body through

enhanced evaporation. Convective ventilation uses cooler night air to cool down the

internal space, preparatory to the hotter times during the day.

Natural ventilation requires the provision of designed openings in the building’s envelope.

The size and position of these openings will influence the effectiveness of ventilation

161

generation. Three types of natural ventilation can be incorporated into a building design.

Cross ventilation is the most common form and utilizes window and door openings placed

in the walls of the building. Depending on wind direction, air will move into the building

through openings in one wall and will travel across the space to exit the building through

openings in another wall. Air circulation within the space is affected by space divisions and

partitions. Optimal cross ventilation will be achieved when inlet openings are present in a

windward wall and outlet openings are located in the leeward wall. Optimal conditions are

not always possible and some cross ventilation will occur even if both the inlet and outlet

are located in the same wall.

Stack ventilation occurs when cooler outside air enters the space preferably through low

level inlets. This air is heated within the space, it then rises and is allowed to exit through

high level outlets causing more inlet air to be drawn into the space. The stack effect is

reliant on a difference in the height of the positioning of the outlet in relation to the inlet.

Maximum effect is achieved with maximum height differential. The effect can be induced

using double hung windows but to achieve a significant effect, outlets are often positioned

in the roof, which also allows the use of roof ventilators to enhance the exhausting o f the

heated air. A reversal of the stack effect is the mechanism that produces the cool air

distributed by a cool tower.

A ventilated envelope is the third form of natural ventilation. This utilizes the stack effect

mechanism, but instead of air being drawn into the space, it is drawn into the envelope

itself. A double layer form of construction is used and ventilation is induced between these

layers. This reduces the build up of heat across the envelope by venting some of it to the

outside.

162

The basecase utilizes all three forms of natural ventilation. Large sliding windows are

situated in the northern and southern facades to allow half the overall glazed area to be

opened and used as ventilation inlet and outlets when required. Apart from the withdrawal

space, the home base block is open plan, therefore cross ventilation is further enhanced by

the lack of partitions and divisions within the space. Stack effect ventilation is induced by

the addition of outlets situated in the ridge of the roof and aided by a cathedral ceiling

and roof ventilators positioned externally. The roof itself is a ventilated envelope, with air

being drawn up the slope of the roof from ventilation inlets at the eaves to the ventilators

at the ridge. Internal ventilation is addressed by the installation of ceiling fans that can be

used to increase the rate of air movement when conditions are hot.

No additional ventilation strategies were simulated as the existing design has extensive

systems already in place.

Infiltration involves air movement through undesigned openings in the envelope. Usually

the term infiltration refers to outside air infiltrating into the space, while exfiltration is

used to specify air that is moving through the envelope from the inside to the outside. This

movement is driven by wind and temperature variations and will often provide the main

source of outside air in envelope-dominated buildings. Infiltration due to its uncontrolled

nature has the most unpredictable influence on thermal conditions. The transferal of air via

infiltration and exfiltration occurs when climatic conditions are unfavorable for thermal

comfort.

The laws of thermodynamics partially regulate infiltration flow rates. During winter

months air will flow from the heated interior to the cooler exterior, whilst in summer this

flow will reverse with heated exterior air flowing into the cooler interior. Both these

situations are deleterious to regulating the thermal state of the building. For this reason

163

infiltration and exfiltration need to be minimized as much as possible. Newer construction

techniques have resulted in increasingly air tight buildings, but a complete seal is almost

impossible to achieve and would be undesirable in buildings not utilizing a HVAC system.

Air exchange needs to occur at a sufficient rate to maintain a supply o f fresh air. A

compromise is required between the rate of infiltration sufficient to maintain air quality

and a rate that does not adversely affect thermal comfort.

164

E n d n o te s

1 DA*SketchPAD2.0, www.arch.utas.edu.au2 Bradshaw, p93.3 Bradshaw, p94.4 Bradshaw, p94.5 Bradshaw, p94.6 Bradshaw, p94.7 Bradshaw, p94.8 Bradshaw, p i00.9 Bradshaw, p95.10 Bradshaw, p i36.11 Bradshaw, p i36.12 Bradshaw, p i37.13 Bradshaw, p i36.14 Ballinger, 1997, p79.15 Ballinger, 1997, p79.16 Calpas, Berkeley Solar Group.17 Lechner, pi 10.18 DA®SketchPAD2.0, www.arch.utas.edu.au19 ASHRAE, p23.1.

165

Conclusions

An analysis of energy usage within schools shows that there is a heavy reliance on it to

provide light and heat within the classroom.

This report has sought to analyze this usage and propose strategies for saving energy in the

visual and thermal environments.

In undertaking this study an attempt has been made to gain insight into facets of

architecture that affect energy usage in a classroom utilizing the bioclimatic equation, as

presented by Szokolay, that:

Given Conditions - Comfort Conditions = Required Controls

This equation was applied to an existing classroom prototype in Sydney, Australia.

A brief description is given of the education system in Australia over the past 210 years.

A detailed analysis of the climatic conditions experienced in Sydney, Australia shows that

Sydney has a temperate climate but can experience hot summers and mild winters.

Heating is the predominant climatic modifier required, but not to any great extent.

Sydney does not experience sub-zero temperatures because of its coastal location.

An overview is given of the conditions within the visual and thermal environments that are

most conducive to a learning situation.

166

The conditions required for a comfortable visual environment within a classroom include

sufficient illumination, an exclusion of glare and the establishment of a space in which

children can easily view their work, regardless of the task or where it is occurring. The

variability of tasks occurring within a classroom poses the greatest challenge to correctly

defining the requirements of a lighting system.

The establishment of thermal environmental criteria is in many ways easier, because the

body reacts biologically to the thermal conditions within a space. The definition of

thermal comfort has tantalized and captured the imagination and curiosity of biological

designers for the last four decades and beyond, with extensive research being conducted

into it. As a result tools, such as the Building Bioclimatic Chart, have been developed to

simplify the quantitative presentation of required thermal comfort conditions. Research

has focused on the thermal comfort of adults with little research being conducted

exclusively with children. Children constitute the majority of occupants in a classroom and

although it is unlikely that they will react in a markedly different manner to adults, further

research is indicated.

Defining the required visual and thermal conditions provides a benchmark against which

the basecase and subsequent strategies can be tested. The basecase used for this report was

a prototype classroom block designed by the Schools Division of the New South Wales

Department of Public Works. It constitutes a Learning Unit, comprised of two homebase

classrooms, a shared withdrawal space and associated auxiliary spaces. Each classrooms has

its own practical activities area and storage areas. An initial analysis of the basecase was

undertaken in relation to both the visual and thermal environments.

167

Required Controls are the product of the bioclimatic equation. Once the given conditions

and the comfort conditions have been established, the difference between the two

constitutes the conditions that require some form of control.

The visual and the thermal environments can be controlled by active or passive means. In

order to provide a visual environment that satisfies the requirements of a classroom, it is

necessary to employ an active system in the form of electric lighting or a passive system in

which naturally occurring daylight is filtered through and controlled by the building

envelope. A third alternative involves a hybrid of the two systems. In the study the last

option was found to provide the best compromise for the efficient use o f energy and the

provision of a good visual environment.

A basic electric lighting system required twenty four 65W fluorescent tubes to light the

basecase space to an illuminance of 320 lux. The correct choice of a luminaire will ensure

that there is no glare associated with these lamps.

Toplighting systems were the most beneficial strategies to investigate because they take

advantage of the fact that the space is single story and because they are not detrimentally

impacted by changes in location of the prototype.

O f the series of systems tested, a monitor type provided the best light distribution

throughout the space. This system was also able to provide the maximum required

illumination value of 320 lux for at least 90% of the work year. A secondary electric

lighting system would provide light in the event that the natural light is insufficient, which

can occur on very cloudy days and when the classroom is used at night. A considerable

saving is achieved when the electric lighting system is only used for approximately 10% of

the work year. Systems are available that integrate an electric system with a daylighting

168

one, controlling the amount of electric light dependent on the quantity of daylight

available, this integration would require further research

When considering the thermal environment the same division exists between active and

passive systems. An active system uses electricity to power the method of adding or

subtracting heat from the space. Passive systems rely on the design of the building

envelope to control heat gain and promote heat loss when appropriate.

Heating is the primary control required in Sydney. When designing an HVAC system a

series of calculations must be undertaken to ascertain required heating and cooling

capacity. These capacities are based on the assumption of design temperatures which the

system is then sized to accommodate.

The required heating and cooling capacity calculations consider the thermal balance of the

building. The requirement for heating arises from the tendency of the building to lose heat

through transmission and convection. The requirement for cooling arises from solar gain,

transmission gain, natural gain and convection gains. The cooling capacity calculations are

more complex than the heat capacity calculations because the materials of the building can

absorb and store heat. Consideration needs to be made for the nature of these materials.

Passive thermal systems utilize the fabric of the building itself to control and enhance the

thermal environment within the building. In order to increase heating, passive solar

strategies were investigated. While daylighting strategies resulted in increased areas of

glazing mass proved the most important in relation to energy savings. This was because the

basecase did not contain any mass materials in a position to provide storage.

169

The various strategies proposed resulted in energy savings of up to 35%, in both heating

and cooling loads. Ventilation was well designed for in the basecase, with provisions for

both natural cross ventilation and stack ventilation, therefore no further strategies were

investigated.

The homebase used as the basecase prototype for this report was designed to be energy

efficient. Efforts were made to maximize the passive systems that were integrated into the

external envelope and priority was given to maximizing the comfort o f the occupants of

this space.

The optimized case incorporated the monitor system as previously described and an

increase in thermal mass, via the use of tiles, along with the use of Hebei block in place of

the external brick skin. When simulated, these strategies resulted in good daylight

illumination levels and distribution, as well as a 20% decrease in heating load and a 15%

decrease in cooling load. These savings were achieved whilst improving the comfort of the

people inhabiting the space.

In investigating the basecase, this study has sought to gain an understanding of the systems

employed and to propose other systems that could be integrated to improve the basecase.

170

Appendices

Table of Contents

Appendix A: Curriculum ii

Appendix B: School and Class Organization xi

Appendix C: Definitions of Climatic Symbols and Boundaries xiv

Appendix D: Climatic Classification of Sydney, Australia xvii

Appendix E: Building Bioclimatic Chart Calculations xviii

Appendix F: Heating and Cooling Load Calculations xxiv

Appendix G: PLEA 99 Presentation xxx

Endnotes xxxvii l

l

A p p e n d i x A: C u r r icu lu m

The curriculum is the single biggest influence on the way a school organizes itself. The

New South Wales (NSW) Board of Studies, which is a statutory State Government body,

is responsible for overseeing the education of the State’s children and does this through the

development of a state-wide curriculum.

In order to facilitate the formulation of this curriculum, a series of guiding principles have

been established, these are:

• Children learn best when they see purpose in their learning and know the outcomes

they are working to achieve.

• Learning experiences should be responsive to children’s individual needs.

• Children’s learning experiences should assist them to learn more.

• Children’s learning is enhanced when they see connections among their learning

experiences and relate them to their everyday experience.

• Children learn best when they are happy to learn.

• Children’s achievements should be effectively and appropriately recognized.

• Children learn best when concepts of justice and equity govern the learning

environment.

The Board’s stated aim is to provide all children with the “knowledge, skills and

understandings necessary for a satisfying and productive life”.

In developing this set of principles, the NSW Board of Studies is attempting to rationalize

current educational theory as it relates to primary age children. There is a strong focus on

the needs of children as individuals, as “they are encouraged to participate in planning

their learning and thus move towards increasing control over, and responsibility for, their

own learning”1, but this is offset by a societal need, for “their learning [to enable] them to

participate in and contribute more effectively in their world”2and “the development of

positive values and attitudes”3 is encouraged.

From these guiding principles, six Key Learning Areas (KLA’s) have been identified. These

provide a broad grouping of the subjects that children are expected to learn during their

formal education, and constitute what is termed a “well balanced”4 curriculum.

These are:

• English

• Mathematics

• Science and Technology

• Personal Development, Health and Physical Education

• Human Society and Its Environment

• Creative and Practical Arts

For each year they are at primary school, students must gain learning experiences in all

these areas.

The Board, in developing primary syllabuses and curriculum support materials, has sought

to “ensure a K-12 learning continuum that is of the highest standard and supports best

teaching and learning practices”5.

Syllabuses have been produced in relation to each of these KLA’s, detailing aims,

objectives, content and outcomes.

The aims of the syllabus details the benefits the student will gain from undertaking the

study. The objectives provide a more specific statement of intent. Teachers are provided

with direction on the teaching and learning process. The objectives also provide a broad

outline of the knowledge, skills and understandings which are considered fundamental to

a mastery of the subject. The substance of the subject is referred to in the Content, which

includes topics, areas of study, key questions, practices, skills and processes which may be

laid out for the teacher. An Outcome Statement in the syllabus specifies the intended

teaching results and provides a clear indication of the knowledge, skills and

understandings that most students are expected to have gained.

Following is a synopsis of each of the six Key Learning Areas, including the aims of the

subject, and the strands included within the subject.

iv

English K -6

“The aim of English K-6 is to develop students’ ability in using language effectively and

critically, and to encourage positive attitudes towards learning English.”6

Language, which in this case is English, is considered central to a child’s “intellectual, social

and emotional development”7.

The subject is divided into three strands, comprising:

• Talking and Listening

• Reading

• Writing.

M a t h e m a t i c s K - 6

“The aims of Mathematics K-6 are to:

• develop in students favorable attitudes towards, and stimulate interest in,

mathematics;

• develop in students a sound understanding of mathematical concepts, processes and

strategies and the capacity to use these in solving problems;

• develop in students the ability to recognize the mathematics in everyday situations;

• develop in students the ability to apply their mathematics to analyze situations and

solve real-life problems;

• develop in students appropriate language for the effective communication of

mathematical ideas and experiences;

• develop in students an appreciation of the applications to mathematics of technology,

including calculators and computers;

• encourage students to use mathematics creatively in expressing new ideas and

discoveries and to recognize the mathematical elements in other creative pursuits;

• challenge students to achieve at a level of accuracy and excellence appropriate to their

particular stage of development.”8

There are four strands to this subject: the content strands:

• Space

• Measurement

• Number

and the process strand:

• Working Mathematically.9

vi

Science a n d Technology K - 6

“The aim of Science and Technology K-6 is to develop in students competence,

confidence and responsibility in their interaction with science and technology, leading

• an enriched view of themselves, society, the environment and the future, and

• an enthusiasm for further learning of science and technology.”10

This subject concentrates on the process of investigating, the process of designing and

making, and the use of technology.11

This subject is divided into six strands:

• Built Environment

• Information and Communication

• Living Things

• Physical Phenomena

• Products and Services

• The Earth and Its Surroundings.12

P e r s o n a l D e v e l o p m e n t , H e a l t h a n d P h y s i c a l E d u c a t i o n K - 6

“The aim of Personal Development, Health and Physical Education K-6 is to develop in

each student the knowledge, skills and understandings needed to understand, value and

lead healthy and fulfilling lives. In doing so, the syllabus will form the basis for students to

adopt a responsible and productive role in society.

This aim will be achieved by developing in each student:

• self-esteem, social responsibility and well-being:

• movement skills and personal fitness:

• the ability to make informed health and lifestyle decisions.”13

This subject is divided into eight content strands:

• Growth and Development

• Interpersonal Relationships

• Personal Health Choices

• Safe Living

• Fitness and Lifestyle

• Games and Sports Skills

• Gymnastics (Movement Exploration)

• Dance

viii

H u m a n S o c ie ty a n d I t s E n v i r o n m e n t K - 6

“The aim of Human Society and Its Environment K-6 is to develop in students the values

and attitudes, knowledge, skills and understandings that:

• enhance their sense of personal, community, national and global identity; and

• enable students to participate effectively in maintaining and improving the quality of

their society and environment.”14

This is the subject where it is expected that children will learn to analyze, synthesis and

apply knowledge. It seeks to teach children to think critically, make decisions and solve

problems.15

This subject is divided into four strands:

• Change and Continuity

• Cultures

• Environments

• Social Systems and Structures.16

Languages other than English are included as a subset of this subject.

C r e a t i v e A r t s K - 6

“The aim of Creative Arts K-6 is to develop in all students a lifelong commitment to

participate in each of the art forms of Visual Arts, Music, Drama and Dance; value the

personal and shared meanings gained from experiencing the arts; and appreciate the role of

the Visual Arts, Music, Drama and Dance in re-affirming, building, and challenging

society and culture.”17

There are four strands within this subject:

• Visual Arts

• Music

• Drama and Dance

A p p e n d ix B: S c h o o l and Class O r g a n iz a t io n

Another of the decisions in determining the use of physical space in a school is the method

of grouping students into classes. Schools usually settle on one of the five standard

systems, or a variation thereof, depending on the size of the school, the number of

students in each age or grade level, the preference and experience of the teaching staff, and

the physical facilities available.

The five systems most commonly used include;

• vertical or multi-aged grouping

• ability grouping by subject

• ability grouping

• parallel grouping

• stratified grouping

Vertical grouping involves placing students of varying ages and school levels into one class.

This is believed to most closely mirror a family situation, with older and younger students

working together.

When the ability grouping by subject system is used, children are placed in a class group

for the study of a specific subject, according to ability in that subject. The group they are

placed in for English, may not be the same as the one they are placed in for Mathematics.

A more general version of this process is ability grouping, where children are “streamed”

according to ability, but only one grouping is used for all subjects. This method results in

“A” and “B” classes, which have been shown to be detrimental to some children’s self­

esteem. It is sometimes referred to as a ‘homologous’ system, because all children of like

ability are grouped together.

In contrast is a parallel group structure. The students in each grade are divided into classes

in such a way that ability is evenly distributed. This results in a “heterogeneous” grouping

with children of widely differing ability being grouped together. This type of class is

difficult to teach because of the wide range of ability present in the class.

Stratified grouping is a hybrid of the preceding two systems, which aims to limit the

extremes present in a parallel class, while incorporating more diversity than is present in an

ability grouped class. In this system children are ranked according to ability and then

divided into groups, the size of which is dependent on the overall size o f the grade. These

groups are then distributed to teachers in such a way as to achieve diversity. A grade of 60

students would be ranked by ability into six groups of ten. Groups one, three and five

would be assigned to one teacher, and groups two, four and six to another. The range of

ability present in each class is reduced but diversity is still present. Similarly there is no

obvious top or bottom class, and teachers do not have to cope with the special needs of the

top and bottom ten students simultaneously.

The size of classes in New South Wales primary schools is set at a maximum of thirty five

students. The actual number in any class is a product of school enrollment. In the public

system, teachers are allocated according to number of students, therefore classes can

become large before additional teachers are available. Funding will also have an effect on

class size.

Xll

Class T i m e t a b l i n g

The method of timetabling used to organize the school day is related to the school and

class organization system in use. The three patterns most commonly adopted are:

• the traditional system,

• the integrated day,

• the mastery concept.

The traditional system uses “fixed allocation of time for particular subjects”18. The

integrated day treats time “as a fixed medium or context for free-ranging activity by

pupils”19, while the mastery concept views time “as a major variable in learning, and

different times are allowed to different students to achieve mastery in the same tasks”20.

xiii

A p p e n d ix C : D e f in i t io n s o f C lim a tic S y m b o ls a n d B o u n d a r ie s 21

C l i m a t i c S y m b o l s

A = killing frost absent: in marine areas, cold month over 18.3°C

r= (rainy) 1 0 - 1 2 months wet: 0 - 2 months dry.

w= winter (low-sun period ) dry; more than 2 months dry.

s= summer (high-sun period) dry; rare in A climates.

B = evaporation exceeds precipitation.

Boundary,

R = 1/2 T - 1/4 PW

where;

R = rainfall, in.

T = temperature, °F.

PW = % annual rainfall in winter half year.

Desert / Steppe boundary is;

R = 1/2 T - 1/4 PW

2

W= desert or arid.

S= steppe or semiarid.

h= hot; 8 months or more with average temperature over 10°C.

k= cold; fewer than 8 months average temperature above 10°C.

s= summer dry.

w= winter dry.

xiv

C = 8 to 12 months over 10°C; coolest month below 18.3°C.

a= hot summer; warmest months over 22.2°C.

b= cool summer; warmest month below 22.2°C.

f= no dry season; difference between driest and wettest month less than required

for s and w; driest month of summer more than 3 cm.

s= summer dry; at least three times as much rain in winter half year as in summer

half year; driest summer month less than 3 cm.; annual total under 88.9cm.

w= winter dry; at least ten times as much rain in summer half year as in winter half

year.

D = 4 to 7 months inclusive over 10°C.

o= oceanic or marine; cold month over 0°C [ to 2°C in some locations inland].

c= continental; cold month under 0°C [ to 2°C in some locations inland].

a= same as in C.

b= same as in C.

f= same as in C.

s= same as in C.

w= same as in C.

E = 1 to 3 months inclusive over 10°C.

F = all months below 10°C.

t= tundra; warmest month between 0°C and 10°C.

1= icecap; all months below 0°C.

XV

C l i m a t i c B o u n d a r i e s

A / C boundary = equatorial limits of freeze; in marine locations the isotherm of 18°C for

the coolest month.

C / D boundary = 8 months 10°C.

D / E boundary = 4 months 10°C.

E / F boundary = 10°C for warmest month.

t / i boundary in F climates = 0°C for warmest month

B / A , B / C , B / D , B / E boundary = evaporation equals precipitation.

BS / BW boundary = one half the above boundary,

h / k boundary in dry climates = same as C / D.

Do / Dc boundary = 0°C [ to 2°C ] for coolest month.

xvi

A p p e n d ix D: C l im a t ic C lass i f i ca t ion o f Syd ney , Austra l ia

Trewartha Classification Sydney Data

C = 8 to 12 months over 10°C all months, Jan to Dec, mean

temperature above 10°C

coolest month below 18.3°C coolest month, July, mean

temperature 12.8°C

f = no dry season lowest monthly precipitation,

Sept, 70mm

highest monthly precipitation,

April, 131 mm

61mm difference

driest month of Summer more than driest month of Summer, Dec,

3cm of rain 80mm (8 cm)

a = hot Summer, warmest months over warmest months, Jan and Feb,

22.2°C mean temperature over 22.2°C,

Oct to April, maximum

temperature over 22.2°C

A p p e n d ix E: B u i l d i n g B io c l im a t i c Chart C a lcu la t ion s

T h e r m a l C o m f o r t C a lc u la t io n P r o c e d u r e 22

The comfort zone can be plotted on the psychrometric chart using the following

procedure:

1. find the annual mean temperature, Tav

2. find the thermal neutrality, T n

Tn = 17.6 + 0.31 x Tav (such that 18.5 < Tn < 28.5°C)

3. plot this Tn on the chart, on the 50% RH (relative humidity) curve

4. mark the lower and upper limits on the 50% RH curve

Lower = Tn - 2°

Upper = Tn + 2°

5. draw the corresponding SET lines, as the side boundaries

SET slope = 0.025 x (DBT -14) for each g/kg of vertical distance

6. mark the upper AH (absolute humidity) boundary at the 12 g/kg level and the lower

boundary at the 4 g/kg level.

This comfort zone will be valid for lightly clothed people at sedentary work. For heavier

physical activities the Tn should be adjusted:

for light work (210W): - 2 K

for medium work (300W): - 4.5 K

for heavy work(400W): - 7 K

xviii

T h e r m a l C o m f o r t C a l c u l a t i o n s f o r Sydney

1. Annual Mean temperature (Tav)Max. Temperature (12 months)

Min. Temperature (12 months)= 22.025 = 13.97

Tav II 00 n

2. Thermal neutrality (Tn)

TnTn

T n (adjusted for light work)

= 17.6 + 0.31 x Tav

= 17.6 + 0.31 x 18 = 23.18 °C

= 23.2 °C = 21.2 °C

4. Upper and Lower temperature limits Lower Lower

= Tn - 2 = 2 1 .2 -2

= 19.2 °C

UpperUpper

= Tn + 2

= 21.2 + 2

= 23.2 °C

5. SET slope calculations SETSET (Lower)

= 0.025 x (DBT -14) = 0.025 x (19.2 - 14)

= 0.13 K/ (g/kg)

SET (Upper) = 0.025 x (23.2 - 14) = 0.23 K/ (g/kg)

C o n t r o l Z o n e C a lc u la t io n s

Passive so lar h e a tin g

daily useful solar gain = daily heat loss

Dv x A x eff = q x (Tn - To) x 24

A = area of solar window

eff = efficiency of the passive solar system

q = specific heat loss rate of the building

Tn = neutrality temperature

To = outdoor temperature limit

July (coldest month)

A = 20%

eff = 0.5

q = 115 W/K

Tn = 21.2 °C

Dv x 20 x 0.5 = 115 x (21.2 - To) x 24

To = 21 .2 -0 .0036 xD v

Dv = 3972

To = 2 1 .2 -0 .0 0 3 6 x 3 9 7 2

= 6.9 °C

x x

M ass e ffec t

Summer (February hottest month)

(Tmax - Train of hottest month)

pt 5s: 12 g/kg AH level at a DBT of:

T5s = T2 + 0.5 x (Tmax - Train)

T5s = 22.5 + 0.5 x (25.5- 18.9)

= 25.8 °C

pt 6s: 4 g/kg AH level at a DBT of:

T6s = T5s + 0.2 x (T5s -14)

T6s = 25.8 + 0.2 x (25.8 - 14)

= 28.2 °C

pt 7s: 14 g/kg AH level at a DBT of:

T7s = T5s - 0.05 x (T5s -14)

T7s = 25.8 - 0.05 x (25.8 -14)

= 25.2 °C

Winter (July coldest month)

(Tmax - Train of coldest month)

pt 5w: 12 g/kg AH level at a DBT of:

T5w = T1 - 0.5 x (Tmax - Train)

T5w = 18.7 - 0.5 x (17.1 -8 .4)

= 14.4 °C

pt 6w: 4 g/kg AH level at a DBT of:

T6w = T5w - 0.2 x (T5w -14)

T6w = 14.4 - 0.2 x (14.4 -14)

= 14.3°C

x x i

A ir m o v e m e n t e ffec t

Temperature depression (dT) = 6 x v - v2

for 1 m/s velocity dT = 5 K

pt 8 dT = 5 KT8 = T 2 + dT

T8 = 22.5 + 5= 27.5 °C

pt 9: 4 g/kg AH level at a DBT of:

T9 = T8 + 0.1 x (T8 -14)

T9 = 27.5 + 0.1 x (27.5 - 14) = 28.9 °C

pt 10: at a DBT equal to T l , on the 90% RH curve

SET = 0.025 x (T8 -14) per unit AH

SET = 0.025 x (27.5 - 14)= 0.34 YJ g/kg

x x i i

30

Q Thermal Comfort Zone

Ml Passive Solar Gain

"l Mass Effect

Air Movement Effect

Fi gure E.O 1: Bu i l d i ng B i o c l i ma t i c C h a r t ( i n c l u d i n g c o n t r o l zones )

xxiii

A p p e n d ix F: H e a tin g and C o o l in g Load C a lcu la tio n s

H e a t i n g L o a d C a l c u l a t i o n s 23

Step 1:

Take off net area of fenestration, opaque walls, roof and floor (area or perimeter)

from building plans or from the actual building (inside dimensions).

Step 2:

Determine design criteria.

A. Select the design outdoor temperature, wind speed, and wind direction.

B. Select the design indoor temperature.

Step 3:

Determine the “coefficient of transmission” (U-factor) for all elements of the

building envelope-fenestration, walls, roof, floors, etc.

Step 4:

Calculate transmission heat loss through each exterior surface:

Load = net area x U-factor x AT.

Step 5:

Determine outside air load due to ventilation , infiltration, or special exhaust:

Load = CFM (liters/sec) x 0>A> factor x AT.

Step 6:

Add up all heat losses.

x x i v

Heating Load Calculations

Inside Design Temp 22Outside Desij%n Temp 5.6Difference 16.4

Item Quantity x U-value x T = W

Glass 36.40 3.50 16.4 2089.4Net Wall (brl 88.65 0.77 16.4 1119.5Net Wall (mt 66.20 0.35 16.4 380.0Roof 207.00 2.00 16.4 6789.6Floor 190.00 1.43 16.4 4455.9Doors 8.50 1.22 16.4 170.1Outside Air 18417.00 1.20 16.4 362446.6

377451

Notes:Bradshaw p 577O.A. 1.5 AC/H

1069 m3/H AC/H xVol /0 .001 (60)17817 1/s

Vent 8 1/s/p Bradshaw p580600 I/s est 75 people

total O.A. 18417 1/s

Bradshaw p 33Summer 23-26Winter 20-22

Bradshaw p 5103Lat Long Elevation Winter

Mean 99% 97.50%Sydney 33 52 S 151 12 E 138 38 40 42

3.3 4.4 5.6

Summer1% DDB 2.5% DDB 5% DDB Mean Rang 1% DWB 2.5% DWB 5% BWB

89 84 80 13 74 73 7231.7 28.9 26.7 7.2 23.3 22.8 22.2

Prevailing WindsWinter Knots SummerN 8 NE

XXV

C o o l in g L o a d C a l c u l a t i o n s 2*

Step 1:

Take off net areas of fenestration, opaque walls, and roof from building plans or

from the actual building (inside dimensions). Areas should be tabulated separately

for each orientation (north, south, east, west, etc)

Step 2:

Determine design criteria:

A. Select the design outdoor temperature and humidity conditions

B. Select the design indoor temperature and humidity conditions

C. Select the hour of peak load by finding the dominant load (south glass, west

glass, roof, internal gains, etc.) and then determining by visual inspection of the

appendix tables or by knowledge of the building operation schedule when the

dominant load will peak.

Step 3:

Determine the solar heat gain factors and shading coefficients of the fenestration

on each exposure (north, south, east, west and horizontal) and calculate the solar

load.

Step 4:

Determine the U-factor of fenestration, opaque walls, and roof. Calculate

transmission heat gains through each exterior surface:

Load = net area x U-factor x AT.

A. Fenestration AT = DB temperature - inside DB temperature.

B. Opaque walls and roof AT = respective sol-air temperature - inside DB

temperature

x x v i

Step 5:

Determine the sensible internal heat gain due to people, lights, equipment, etc.

Step 6:

Determine the sensible heat gain from outside air:

Sensible load = L/s - O.A. factor - AT

Step 7:

Add all loads from Steps 3 through 6 to obtain the total sensible load.

Step 8:

Determine the latent internal loads due to people and other sources of moisture.

Step 9:

Determine the latent load due to outside air.

Step 10:

Add up all loads from Steps 8 and 9 to obtain the total latent load.

Step 11:

Determine the total load by adding the results of Steps 7 and 10.

x x v i i

Cooling Load Calculations

Space use School ClassroomsFloor area 189.7Volume 712.7Peak Load Date DecTime 12:00Hrs/Day of Op 15Glazing singleShading overhangsWall Color darkRoof Color lightLatitude 33 52 S

Conditions DB WB % RH DP Hum RatioOutdoor 28.9 22.8 15Room 23 50 9Difference 5.9 6

Sensible LoadsSolarExposure Area x SHGF x SC X TLF = WN 14.53 191 0.64 0.59 1048E 1.26 134 1 0.76 128S 15.28 128 0.64 0.76 951W 1.26 134 1 0.76 128

2256

Transmission Area x T x U-value x TLF = WExposureGlass 32.33 5.9 3.5 1 668WallsN-brk 26.22 31.7 0.77 0.28 179N -m tl 13.3 19.3 0.35 0.28 25E-brk 21.1 14.9 0.77 0.35 85E-mtl 19.8 11 0.35 0.35 27S-brk 22.23 14.3 0.77 0.6 147S-mtl 13.3 10.3 0.35 0.6 29W -brk 21.1 14.9 0.77 0.35 85W -mtl 19.8 11 0.35 0.35 27Roof 207 27.7 2.00 0.37 4243Doors 11 11 1.22 0.35 52

5565

x x v i i i

O.A.Inf/Vent x 1.2 x C = W

18417 1.2 5.9 130392

Internal HeatPeople Number x W (each) x BSF X Diversity = W

70 80 0.84 1 4704Lights W x Ballast X BSF x Diversity = W189.7x32.3 6127.3 1.2 0.8 0.8 4706Equip W X BSF x Diversity = W

1 0Appliances W X BSF x Diversity = W

1 09410

Total Sensible Load = W147623

Latent Loads

People Number x W (each) x Diversity = W70 80 i 5600

Appliances = W0

O. A. L/s x g/kg X 2.808 = W18417 6 2.808 310290

Total Latent Load = W315890

Total Load = W463513

Notes:Sol-air temps

dark lightS 37.3 S 33.3

E /W 37.9 E/W 34N 54.7 N 42.3R 76 R 50.7

XXIX

A p p e n d ix G: PLEA 99 P r e se n ta t io n

SIMULATION OF DAYLIGHTING STRATEGIES USING A “MIRROR-BOX” ARTIFICIAL SKY

Felicity Lewis, b.a rch . (Hons.) m a r c h .College of Architecture, Planning and L an d scap e A rchitecture University Of Arizona Tucson, AZ, 85719, USA felicityJew is@ hotm ail.com

Abstract

In order to eva lu a te the e f fe c tiv e n e ss a n d su itability o f a particu lar dayligh tin g s tr a te g y for utiliza­tion in a sp ec ific s p a c e , s o m e b a s is for co m p a riso n n e e d s to b e e s ta b lish e d . T he u s e o f p h y s ic a l s c a le m o d e ls a n d an artificial s k y light so u rc e p ro v id e s o n e m e th o d o f a ch iev in g this. A rch itec ts are com fortab le with co n ce iv in g o f s p a c e in m initure a n d a re a d e p t a t g e n e ra tin g th eir d e s ig n s to sca le . W hen th is ability is c o m b in e d with th e technica l a s p e c ts o f p h o to m e tr ie s a n d p h o tograph y, lighting sim ulation resu lts can g e n e r a te inform ation th a t is read ily u tilized .

1 Introduction

This report considers the procedure whereby scale models can be used in conjunction with a form of artificial sky referred to as a “mirror-box”, to simulate the lighting situation within a class­room when different daylighting strategies are applied.

2 Luminous Environment

In order to design and analyze daylighting systems it is necessary to consider the location of the building to determine the specific luminance distribution and the luminance levels available. The product of this analysis is referred to as the design sky, the pa­rameters of which define the variables used in calculations and simulations.

r|

100% r

O cloudy B partly cloudy"clear

This study was conducted using a building location in Sydney, Australia (Lat. 33’ 52” S, Long. 151’ 12” E). In analyzing this location consideration was given to sky type and annual skycloudiness, as well as available illuminance levels. Figure 2.1 charts the occurrence of specific sky types as a percentage of each month. Sydney has predominantly partly cloudy skies, al­

I § H I M 9 §! 8 § 8 IMonths

Fig. 2 .1 : Occurence of specific sky types (Ruck, p20)

XXXI

though a cloudy or overcast sky occurs from 10% to 25% of the time. Illuminance levels indicate the amount of light available from the sky vault. This information is presented a s a percentage of the working year that a given illuminance is exceeded and is graphed in Figure 2.2.

From this data it is possible to formulate a luminous environment classification. The design sky model chosen was the Interna­tional Commission on Illumination (CIE) overcast sky. This sky is defined as having a luminance distribution such that:

I_y = Lz (1 + 2 siny) / 3 where:Ly= luminance at altitude angle y Lz = zenith luminance

This sky, although only occurring for a part of the year, is the worst case scenario. If a system is designed to perform within these parameters, in actuality, performance will be better than de­signed.

In determining exterior luminance levels for calculation purposes, a level of 8500 lux was chosen. The Experimental Building Station (EBS) follows Dresler and Brentwood in setting a lux value that results in daylighting being sufficient to provide the required lighting levels, unaided, for 90% of the working year.

3 Application

Once the luminous environment is defined, design analysis can be undertaken.

The procedure by which light interacts with a space is not a function of scale. Light will enter into and be distributed within a scale model of a space in a manner nearly identical to that which would occur in the building itself (Robbins, p221). Due to this scaleless nature of light, scale models can be used to represent spaces being analyzed.

The other aspect of the development of physical scale modeling is the introduction of artificial skies in order to gain an accurate and consistent light source that closely matched a designated sky type.

The “mirror-box” type artificial sky is a rectangular light tight box of which the interior walls are clad with mirrors and the ceiling composed of fluores­cent lamps and a diffuser panel to provide diffuse light. The multiple inter-reflectance generated by the mirrors creates a simulation of an overcast diffuse sky, with a lumi­ Fig. 3.1: Mirror-box Concept (Szokolay, piu)

100.0

5 20 .0

Diffuse Horizontal Illuminance (klx)

Fig. 2.2: Horizontal illuminance levels as a percentage of working year (Ruck, p42)

x x x i i

nance distribution similar to that of the CIE overcast sky. Figure 3.1 illustrates the “mirror-box” concept.

To produce useable results, the variables within the scale model that affect light penetration and distribution need to be accurately rendered. Interior surfaces need to have a reflectance similar to that of the actual space, and apertures need to be sized and placed correctly. Depending on the type of research being conducted, interior fixtures and furnishings can be included, but are not essential to overall general readings.

When a scale model is placed in the “mirror-box”, photometric and photographic results can be generated for analysis.

3.1 Photometric Analysis

The design of daylighting systems involves analyzing both the quantity and quality of the light that pen­etrates into, and is distributed within, the space.

Photometric analysis provides information related to the quantity of light available at specific points within the space. Light sensors are used to m easure the light levels achieved by the various systems being studied. Figure 3.2 indicates the location of the sensors within the study model.

From these sensor readings graphs can be generated to indicate the distribution of light within the space and the variation in light levels across the space. The quan­tity of light can be m easured as an illuminance level or as a factor of available exterior daylight.

3.2 Photographic Analysis

The quality of light within a space is as important as the quantity of light. The way in which light interacts with the physical design elem ents of the room will influence the success of a daylighting system.

Photographic analysis involves photographing the interior of the scale model in such a way that the space can be conceived as if it was being viewed at full scale. The photographs reproduced in this report were taken using a 28mm lens, set so that eye level was consistent with the scale model.

These images graphically indicate the nature of the light within the test space.

Fig 3.2: Location of Light Sensors

xxxm

4 ResultsAn analysis was conducted of three top-lighting systems as applied to a prototype classroom design. Initially the basecase system of skylights was evaluated. Then a basic sawtooth system and monitor system were designed and tested.

The photometric results of this investigation are presented in the form of daylight factor (DF) graphs. The Australian Standard (AS1680.1-1990) requires that “design ( of a daylighting sys­tem) should be based on a daylight factor capable of providing 200 lux or more throughout 90% of normal working hours” (AS1680.1-1990, p60). With an external luminance level of 8500 lux, this equates to a daylight factor of 2.35%, which is a little higher than the early recommendations of a 2% daylight factor in classrooms (Szokolay, p 142). The required illumination levels as specified in AS1680.2.3-1994 are 240 lux in a general classroom, increasing to 320 lux in a reading room.

Generally, due to the assumptions made concerning exterior luminance levels, daylighting sys­tems will produce significantly greater interior illumination levels than the design baseline.

4.1 B asecase

The basecase is a homebase classroom block which is part of the Component Design Range of prototype school buildings designed by the New South Wales Department of Public Works and Services. The space is an open-plan classroom with an attached practical activities area and a shared withdrawal space. The classroom is approximately 8 m x 8 m, with the practical activities area being approximately 3 m x 6 m.

A top-lighting strategy is currently part of the design of the building. It consists of a series of strip skylights that run perpendicular to the ridge of the roof. These skylights were created by replacing part of the corrugated roof sheeting with panels of a polyester translucent roof sheeting. The space has a cathedral ceiling and directly below the translucent sheeting, a dif­fuser panel is set in line with the ceiling lining.

Figure 4.11 indicates the light levels achieved by this system. The values are low, although they are uniform. These skylights were designed to work in conjunction with large windows, and were not conceived as an isolated solution.

Figure 4.12 illustrates the low light levels occur­ring within the space. The skylights are unobtru­sive and generally the ceiling is less dominant with this type of system. Glare is not a problem, due in part to the small amount of glazing used and the use of layers of diffusing materials.

Fig. 4.11: Photom etric resu lts: B asecase

Fig. 4.12: Photograph resu lts: B asecase

xxxiv

4.2 Saw tooth System

The sawtooth system analyzed consisted of a series of four rooflights equally spaced across the depth of the room, with the glazed areas oriented North.

Figure 4.21 graphs the photometric results for this strategy. The graph displays the classic increase in lighting levels under successive apertures. This system produced the greatest luminance levels, especially against the South wall. A steady increase in light levels occurs across the space.

Figure 4.22 graphically demonstrates the advan­tages and disadvantages of this type of system. Light appears to be fairly evenly distributed within the space and the ceiling is well illumi­nated. The apertures have been extended to the side walls so that these walls receive high levels of light, although there is some shadowing related to the rhythm of the apertures. One of the problems associated with this system is glare as evidenced by the large, bright areas of glazing within the viewers field of vision.

. a -l.

Z7._vz»T

\ Z 3

Fig. 4.21: Photom etric resu lts: Saw tooth

Fig. 4.22: P hotographic resu lts: Saw tooth

4.3 Monitor System

The monitor system studied comprised a series of four monitors spaced evenly across the depth of the room. The glazing in this system faces North and South. These monitors are placed relatively close together and therefore have a high glazed area to floor area ratio.

.... A*A- _JSA_̂___ 2%

, * \

Figure 4.31 indicates the light values obtained when this system was tested. The light levels are significantly higher than those achieved by the basecase system and show a more uniform distribution than the results from the sawtooth system. The nature of the monitor system is bi­directional light penetration and significantly different results would be obtained if this system was tested under a clear sky situation.

Figure 4.32 displays the uniformity of light distribution within the space. The wall does show evidence of shadowing associated with the spacing of the monitors. Glare is apparent with this system, although less glazing is ex­posed than with the sawtooth system.

Fig. 4.31: Photom etric resu lts: Monitor

Fig 4.32: Photographic resu lts: Monitor

xxxv

5 Conclusion

Physical scale modeling allows a range of daylighting systems to be evaluated efficiently. The use of an artificial sky maintains a consistent situation within which to test these models. The “mirror-box” sky effectively imitates the lighting situation experienced when there is an overcast sky.

The ability to generate both photometric and photographic results from scale models allows the designer to consider the quality and the quantity of light that will be created in the space under investigation.

7 References

A ustralian S ta n d a rd 1 6 8 0 .1 -1 9 9 0 Interior lighting P art 1: G en era l p r in c ip les a n d re c o m m e n d a ­tions, Sydney, Standards Australia, 1990

A ustralian S ta n d a rd 1 6 8 0 .2 .3 -1 9 9 4 Interior lighting P art 2: R e c o m m e n d a tio n s for sp ec ific ta sk s a n d interiors, Sydney, Standards Australia, 1990

Robbins, Claude L , D aylighting: D esig n a n d A n alysis , New York, Van Nostrand Reinhold Com­pany, 1986.

Ruck, Nancy C., S kyligh t A vailab ility in A ustralia: D ata a n d Their A pplica tion to D esign , Sydney, Illuminating Engineering Society of Australia, 1985.

Szokolay, S. V., E n viron m en ta l S c ie n c e H an dbook for A rch itec ts a n d Builders, Lancaster, En­gland, The Construction P ress Ltd., 1980.

x x x v i

E n d n o t e s

1 Barcan ,p 8.2 Barcan ,p 8.3 Barcan ,plO.4 Barcan ,p 17.5 Barcan ,p 8.6 Barcan ,p 19.7 Barcan ,p 19.8 Barcan ,p 21-22.9 Barcan ,p 23.10 Barcan ,p 24.11 Barcan ,p 25.12 Barcan ,p 26.13 Barcan ,p 27.14 Barcan ,p 29.15 Barcan ,p 30.16 Barcan ,p 30.17 Barcan ,p 33.18 Bassett, p207.19 Bassett, p207.20 Bassett, p207.21 Trewartha, p250-251.22 Szokolay, 1987, pl3.23 Bradshaw, p95.24 Bradshaw, p95.

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