TVE 12 011 maj

Examensarbete 15 hpJuni 2012

Exergy Analysis of two Residential Buildings with Wooden and Concrete Frame

Maria LidholmCamilla OdelbrinkJosefin Sandwall

Teknisk- naturvetenskaplig fakultet UTH-enheten Besöksadress: Ångströmlaboratoriet Lägerhyddsvägen 1 Hus 4, Plan 0 Postadress: Box 536 751 21 Uppsala Telefon: 018 – 471 30 03 Telefax: 018 – 471 30 00 Hemsida: http://www.teknat.uu.se/student

Abstract

Exergy Analysis of two Residential Buildings withWooden and Concrete Frame

Maria Lidholm, Camilla Odelbrink, Josefin Sandwall

In this thesis, the exergy consumption for two concepts of residential buildings,wooden frame and concrete frame, are studied from a life cycle perspective. Focuslies on evaluating building constructions suitable for sustainable city districts. The cityof Uppsala is in the phase of planning for such a district, where Järntorget is one ofthe selected constructors. Since the district in Uppsala still is in a planning state, theconcepts examined in this thesis are two ongoing projects, led by Järntorget. The lifecycle of the thesis includes four phases; raw material extraction, production of thematerial, construction of the building and the building’s operation phase. The fourphases are divided into three groups and an analysis of the exergy demand in everygroup is made. Group 1 includes the extraction, production and transportation of thematerial, group 2 includes construction of the building and group 3 includes theoperation phase of the building. An Excel sheet has been created to calculate theprimary exergy demand within group 1 and 2 and the modeling tool Annex 49 hasbeen used to calculate the exergy use within group 3. The result shows that awooden frame concept is the concept with lowest exergy demand, when summarizingall phases. The largest impact on the exergy consumption occurs during the operationphase, which implies that the heating of a residential building is the most exergydemanding process during the life cycle of a building. Since heat is of low exergy, it issubstantial to use low-exergy sources for the building’s heating purpose to ascertain aminimum of exergy loss. The exergy analysis shows that the exergy efficiency is lowerthan the energy efficiency in group 3, demonstrating that the exergy approach gives adeeper insight to efficient usage of resources.

ISSN: 1650-8319, UPTEC STS12011Examinator: Joakim WidénÄmnesgranskare: Magnus ÅbergHandledare: Anders Hollinder

Occurring Terms and Abbreviations

Ballast Ballast is one of the components in concrete.

It consists of rock, usually sand, gravel or

stone.

Cement Cement is one of the components in concrete.

It consist mostly of limestone that is burned

and then grinded.

CHP Combined Heat and Power. Refers to a power

plant producing both heat and power.

kWh Kilo Watt hour. In Sweden, a commonly used

unit for energy and exergy. 1 kWh equals

3600 Joule.

Primary energy An energy form found in nature that has not

been subjected to any conversion or

transformation process. For example crude oil

and solar energy.

Primary factor Secondary energy carriers, for example

electricity, are generated with the help of a

primary energy source. As some heat losses

are created in the transformation, a higher

amount of primary energy is required to

achieve a certain amount of secondary energy.

The conversion factor for this process is the

primary factor.

Psi-value Describes how well linear thermal bridges

conduct heat. A low value indicates good

insulation.

Solar constant Total solar insolation per unit area.

Thermal bridge When a design component in a building is in

contact with the colder outside. This can

lead cold to the warm inside or vice versa. In

this area, the thermal conductivity is higher

than of the surrounding material.

U-value Describes how well a building element

conducts heat.

4

Table of contents 1. Introduction ___________________________________________________________ 6

1.1 Aim of the Report _____________________________________________________ 7

2. Background ___________________________________________________________ 8

2.1 The Exergy Concept ___________________________________________________ 8

2.2 Sustainable City Districts _______________________________________________ 8

2.3 District Heating _______________________________________________________ 9

2.4 The Power Systems of Sweden and Europe _______________________________ 10

2.5 Construction Materials ________________________________________________ 11

2.5.1 Wooden Frame __________________________________________________ 11

2.5.2 Concrete Frame _________________________________________________ 12

3. Methodology __________________________________________________________ 14

3.1 Life Cycle Approach __________________________________________________ 14

3.1.1 Delimitations ____________________________________________________ 15

3.2 Models ____________________________________________________________ 15

3.3 Collecting Data ______________________________________________________ 16

3.4 Definition of Exergy __________________________________________________ 16

3.4.1 The exergy content of electricity _____________________________________ 18

4. Data _________________________________________________________________ 19

4.1 Data for Group 1: Extraction, Production and Transportation __________________ 19

4.2 Data for Group 2: Construction Phase ____________________________________ 20

4.3 Data for Group 3: Operation Phase ______________________________________ 20

4.3.1 Data for different time perspectives of district heating in Uppsala ___________ 22

5. Results ______________________________________________________________ 23

5.1 Results for Group 1: Extraction, Production, and Transportation _______________ 23

5.2 Results for Group 2: Construction Phase __________________________________ 24

5.3 Results for Group 3: Operation Phase ____________________________________ 25

5.3.1 Results for different time perspectives of district heating in Uppsala _________ 28

5.4 Total Result ________________________________________________________ 29

6. Sensitivity Analysis ____________________________________________________ 31

6.1 Change of life span___________________________________________________ 31

6.2 Change of heating source _____________________________________________ 32

6.3 Change of window position ____________________________________________ 33

7. Discussion ___________________________________________________________ 34

7.1 Sources of Error _____________________________________________________ 35

8. Conclusions __________________________________________________________ 37

References ________________________________________________________________ 38

Appendix A ________________________________________________________________ 41

5

Appendix B ________________________________________________________________ 43

Appendix C ________________________________________________________________ 45

Appendix D ________________________________________________________________ 46

6

1. Introduction Sustainable development is an expression that can be defined in many ways. Today, the

expression is often used as an incitement for preserving the environment for future

generations. One feature of sustainable development is the aspect of energy, how it is

generated and how it is used. Globally, the energy use has increased with more than 20

percent during the last 10 years. A large amount of this energy is used during the

construction of residential buildings. (Swedish Energy Agency 2012)

In Sweden, the Government has set strict targets for emission reduction and energy

efficiency. One way to achieve this is to build so-called sustainable city

districts. The City of Uppsala is currently in the process of planning such a district,

Östra Sala backe. In this area the idea is to test new sustainable building concepts and a

variety of constructors have been chosen to build residential buildings with different

profiles (The city of Uppsala 2012).

Constructors are constantly developing new concepts for sustainable buildings.

Residential buildings with concrete frame are still the most commonly occurring

building concept, though since the early 21th century wooden frame buildings are

becoming more and more common. Wood is often promoted as very environmentally

friendly with low carbon dioxide emissions (Svenskt trä 2012). In Östra Sala backe one

of the constructors, Järntorget, is planning to build apartment complexes with a wooden

frame. Järntorget also use concrete frame in other projects, with an environmental

profile (Järntorget 2012). From a sustainable perspective it is therefore interesting to

compare these different concepts.

To examine environmental impact and energy efficiency there are many different

methods and tools. One of the most commonly used is calculations of carbon dioxide

emissions or primary energy consumption. Sometimes these methods are insufficient

and new tools need to be examined. One of these is exergy analysis which is a method

where the quality of the energy is in focus, thus this method adds the aspect that

matching energy source with type of demand is important.

7

1.1 Aim of the Report

The purpose of the report is to compare two construction concepts for residential

buildings, one with wooden frame and one with concrete frame. The comparison is

made using exergy analysis from a life-cycle perspective to examine the sustainability

of the different concepts.

Question formulations:

Which concept requires the highest amount of exergy?

How do the different phases of a building's life cycle affect the exergy

consumption?

How can exergy analysis be a useful tool for examining sustainability,

considering the chosen projects?

8

2. Background The general background to the studied material is presented in this chapter. To ease the

understanding of the used method, the chapter begins with an explanation of the exergy

concept. Section 2.2 describes the concept Sustainable City Districts. This concept is in

focus in the Östra Sala backe project, and is an incitement for this report. In Uppsala,

district heating is widely used, and is also likely to be a supplier of heat in the Östra

Sala backe area. Therefore, district heating is explained in section 2.3. Section 2.4

briefly describes the Swedish electricity system and the environmental evaluation

assessment applied to electricity use in this report. The construction materials and on

site construction is presented in section 2.5.

2.1 The Exergy Concept

Exergy is a concept used to describe the part of the energy that is accessible for

translation to useful work. The unit for exergy is the same as for energy, joule or kWh

for which the latter will be the unit of choice in this report. The fraction of exergy

content expresses the quality of an energy source or flow. This can be used to combine

and compare all flows of energy according to both their quantity and quality.

Unlike energy, which according to the first law of thermodynamics is indestructible,

exergy is always destroyed when a process involves a temperature change or energy

conversions (Energikunskap 2012). This is analogue to the second law of

thermodynamics. The part of the exergy that is destroyed is called anergy (Wall 1986).

There are different forms of exergy carriers, primary and secondary. Primary exergy

carriers derive from natural resources such as crude oil, uranium, sun, wind, and water.

These resources can then be transformed to secondary exergy carriers such as electricity

and heat. In the transformation from primary to secondary, some of the exergy is

destroyed. High-valued energy, such as electricity and mechanical work, consist of pure

exergy. Low-valued energy, such as heat, has limited convertible potential and thereby

low exergy content (Wall & Östlund 1993).

2.2 Sustainable City Districts

Problems with poor air quality, traffic congestion, buildings with poor energy

performance and associated problems are common in cities all over the world. One way

to tackle these problems is to implement sustainable smart cities or city districts

(Environmental Protection Agency 2011). In Sweden, several projects with sustainable

city districts have been implemented. One example is Norra Djurgårdsstaden in

Stockholm, a project under construction with the aim to create a climate positive district

with smart infrastructure solutions and energy efficient buildings (The city of

Stockholm 2011).

In Uppsala, the construction of a similar district called Östra Sala backe is currently in

the planning stage. The idea in this neighborhood is to try out new energy efficient and

9

environmentally friendly building concepts and together with infrastructure

developments make the area innovative, modern and sustainable. The project is

currently in the phase of detail planning and construction of the buildings is planned to

start in 2014 (The city of Uppsala 2011).

2.3 District Heating

District heat is a large scale system for distributing heat generated in a centralized

location for residential and commercial heating, which can be used both for space

heating and hot water. The heat is generated by heating water in plants with either heat-

only boilers or combined heat and power plants (CHP), where both heat and electricity

is produced. The fuel to heat the water can be of many different types, e.g. bio mass,

waste, coal, oil, natural gas, or electricity. The generated heat is transferred as hot water

through a network of pipelines and transported to the consumer. At the consumer, the

heat is transferred by heat exchangers and the chilled water is transported back to the

plant.

In Uppsala, the district heat is delivered by Vattenfall. The heat production utilities in

Uppsala contain both CHP plants and heat-only boilers. The fuel mix for the Uppsala

plants is showed in figure 1. Vattenfall’s aim for the future is to replace peat and coal

with bio mass (Energinyheter 2012). This will decrease the emissions from the system,

since peat is considered a highly CO2 emitting fuel and bio mass is considered to be

CO2 neutral in a time perspective of around 40 to 50 years (Åberg p 37, 2012).

Figure 1. Fuel mix for district heat in Uppsala 2011. (Vattenfall 2012)

Waste 48.8 %

Peat 31.1 %

Wood 7.7 %

Fossil oil 5.8 %

Coal 5.5 %

Electricity 1.1 %

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Figure 2. Future fuel mix for district heat in Uppsala. (Energinyheter)

2.4 The Power Systems of Sweden and Europe

The Swedish power system is a part of the Nordic electricity network which is

connected to the European power system. In the Nordic electricity generation mix,

hydro power is the dominating source. Around 14 % of the mix consists of Nordic fossil

thermal power and the remaining part consists of nuclear and non-hydro renewable

power generation. The European electricity mix is dominated by fossil thermal

electricity followed by nuclear power, hydro and other renewable sources. (Åberg p15,

2012)

The concept of electricity on the margin refers to the power generation plant that, from a

market economic perspective, is the least attractive to run at a certain time. This means

that changes in electricity use affects the most expensive electricity generation plant in

the system, at the moment. Since the Swedish electricity system is connected to the

European system, the production margin in Sweden can be considered to be located

outside the Nordic system (Åberg p 20, 2012). In this report the production margin is

assumed to be constituted of European coal condensing power plants.

Waste 48.8 %

Bio mass 44.3 %

Fossil oil 5.8 %

Electricity 1.1 %

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2.5 Construction Materials

The required materials in the studied construction concepts are mainly wood and

concrete. Since a life-cycle approach is applied, the raw material extraction process is

presented as well as how the construction material is used in the construction phase.

2.5.1 Wooden Frame

Figure 3. Four phases of the life cycle of a wooden frame building.

Figure 3 shows the concerned phases in the process of constructing a wooden frame

building. In 1994 a change in the law for residential buildings was implemented. It

allowed constructions of buildings with wooden frame, provided that the building could

prevent fire spreading with the help of fire doors and has a fire protection around the

supporting structure (Boverket 2012). Wooden frame in residential buildings was

prohibited before 1994, mainly because of the fire hazard. Wooden frame buildings

have an approximate lifespan of 50 to 100 years. (Engelmark 2005)

Modular element is a concept for constructing residential buildings with wooden frame.

It is a cost effective and environmentally friendly way to build; by handling the most

parts of the concept at the same place, minimization of transports and intermediaries can

be made. The concept is called modular element when the frame, floor, wall and roof

components of a building are made and assembled in the same factory. Even electrical

installation, finishing layer and interior design can be completed at the factory. The

usage of modular element is generally a damp-proof construction method, as the

building components usually are assembled in one day. Disadvantages with the usage of

modular element are the vulnerability during movement and relocation, which can cause

cracking. The ability to transport the modular element to the construction place must be

evaluated in advance, so that weight and height of the transports are allowed on the

roads to the construction site. (Träguiden 2012)

•Forest

•Mineral wool

•Energy consumption

Raw material

•Lumber

•Insulation

•Plasterboard

•Energy consumption

Production of the material

•Constructing

•Assembling

•Modular element

•Energy consumption

Construction phase

•Heat demand

•Heat source

•Lightning

•Ventilation

•DHW

•Lifelength

Operation phase

12

Wood has a low thermal conductivity, which leads to small thermal bridges between the

construction parts. The natural resistance in and density of the wood differs, depending

on the quality and type of wood. (Träguiden 2012)

2.5.2 Concrete Frame

Figure 4. Four phases in the life cycle of a concrete frame building.

Figure 4 shows the concerned phases in the process of constructing a concrete frame

building. Concrete contains approximately of 80% ballast, 14% cement and 6% water,

where the cement and water acts as a binding paste. Concrete is produced in concrete

factories, where ballast, cement and water are mixed with chemical substances. The

chemical substances are added to make the concrete handle temperature and weather

changes. (Gillberg et al 1999 p5)

A concrete slab is either prefabricated or produced in situ. Prefabricated concrete is

made in a factory which means it is weather-proof and high quality assured. The seams

are sealed at the construction site. When using in situ concrete slabs the concrete is

poured wet into formworks at the building site. The reinforcement is also made at the

site and the rebars are placed directly into the formwork. In contrast to prefabricated

concrete, the in situ slabs are weather and temperature dependent during the

construction. In larger projects it is common to combine the two methods. (Gillberg at

al 1999 p39-42)

Concrete frame buildings have a long lifespan, often longer than 100 years, and the need

for renovation of a correctly constructed structure is almost non-existent. However, a

need for renovation can occur if the frame is exposed to excessive dampness (Svensk

•Ballast

•Cement

•Water

•Mineral wool

•Energy consumption

Raw material

•Concrete

•Plasterboard

•Steel

• Insulation

•Energy consumption

Production of the material

• Constructing

• Assembling

• Prefabricated and in situ

• Energy consumption

Construction phase

•Heat demand

•Heat source

•Lightning

•Ventilation

•DHW

•Lifelength

Operation phase

13

betong 2012). A concrete frame can withstand fire, without need of extra fire protection

(Betongbanken 2010a).

Due to concrete’s high thermal conductivity, serious thermal bridges can occur between

building components. This means that it is important to strengthen the edge beams with

insulation. (Betongbanken 2010b).It requires a certain wall thickness for a building to

manage temperature change. Building constructions of heavy materials, such as

concrete, does not require the same thickness as constructions of light material, such as

wood. (Betongbanken 2010e) A concrete frame building has generally a lower U value

than a wooden frame building, due to its ability to store heat. (Eskilsson 2008)

14

3. Methodology In this chapter the methodology of the report is presented. Section 3.1 explains the

system and delimitations of the life cycle approach. A constructed Excel sheet as well as

the modeling tool Annex49 and the required inputs for the models are described in

section 3.2. The method for collecting data is presented in section 3.3. Finally, a more

specific definition of exergy and the usage of the concept in this report are defined in

3.4.

3.1 Life Cycle Approach

Figure 3. The five phases of a building’s life cycle.

In the process of creating a building, five phases are required; extraction of raw

material, production of material, construction of the building, the use phase of the

building and demolition. Between these phases, a calculation of the required

transportation is made. This report concerns itself with the first four phases. The four

phases are divided in to three groups, as demonstrated in figure 6, to enable a

summation of the required exergy during a life cycle. This choice of division is made

due to accessible data. The first group includes the extraction, production and

transportation of the material, the second the construction of the buildings and the third

contains the operation phase when the buildings are used. All of these groups are

calculated separately and thereafter summarized to a total amount of required primary

exergy for each building concept. In group three, the exergy and energy demand is

calculated and compared with the required primary exergy and energy input. This

enables a calculation of the exergy and energy efficiency.

Figure 4. The included phases of a building’s life cycle are examined in three groups

and the results from the different groups are then summarized.

Extraction of Raw Material

Production of the Material

Construction Phase

Operation Phase

Demolition Phase

TOTAL AMOUNT OF EXERGY

GROUP 1 Extraction, production

and transportation

GROUP 2 Construction on site

GROUP 3 Operation of finished

project

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3.1.1 Delimitations

Due to a limited time span and access to appropriate data, the report will not include the

demolition phase of a building. This part of the process is the most negligible, based on

previous research looking at energy consumption (Gillberg et al 1999 p70), and is

therefore considered to not have a significant impact on the buildings’ total energy and

exergy use.

Other components inside the system boundaries that fall outside of the aim of this report

are

Outdoor environment, for example constructing green areas.

Fixtures, domestic appliances, and furniture. Heat gains from the appliances and

residents will be subtracted from the total heat demand of the buildings.

Household waste, electricity, water consumption.

The life cycle regarding garage, porch, and other constructions outside the main

building.

These items will not be included as this report mainly concerns the specific building and

its structure, not how it is affected by its occupants. Furthermore the report does not

include any form of economic cost-estimations. Evaluation of other methods for

measuring environmental impact such as green house gas emissions will not be made.

The report does not include other aspects of sustainability such as living standards.

For both concepts, the material for inner- and load bearing walls will be excluded, due

to lack of data. A lifetime of 50 years is assumed for both building concepts, even

though a building is likely to remain even longer than 50 years. This is because different

renovations might be necessary after that time span and the impact of renovation need is

hard to predict and is therefore not taken into consideration in this report. (De Meester

et al 2008)

3.2 Models

To calculate the required exergy for group 1 and 2, an Excel sheet has been created. For

group 1, the different amounts of required material are used as input and with given

parameters of exergy consumption for the different materials, a total amount of exergy

consumption is calculated. The exergy consumption for group 2 is calculated as the

required exergy on site. The results for group 1 and 2 are presented in both tables and

diagrams showing required exergy per m2.

The modeling tool Annex 49 will be used to calculate exergy usage during the

building’s operation phase, group 3. Annex 49 is constructed in Excel and is a tool for

examining the required exergy for heating systems as well as other exergy requiring

systems in a building. Due to a building’s operative energy demand, the exergy losses

will be calculated. (Annex 49)

16

The required energy is calculated by including several inputs regarding the building

envelope. The main inputs are

Volume and net floor area

Area, thermal bridges, and u-value for walls, windows and doors

Climate data

Heating system

Number of occupants

The result of the calculated required exergy of the building during the operating phase is

presented in general values as well as diagrams. An observation of the required exergy

during the operation phase for each month over one year and a final summation is made.

3.3 Collecting Data

Data concerning amount of material and measurement specifics is collected from the

constructor Järntorget. Since the building project in Östra Sala backe still is in the stage

of preparation, the report will examine two other ongoing projects, led by Järntorget.

From the thesis; Life Cycle Primary Energy Use and Carbon Emission of Residential

Buildings by Ambrose Dodoo, data concerning required energy for group 1 and 2; raw

material extraction, production of the material, transport of the material, and the

construction of the buildings are collected. (Dodoo 2011)

To understand the concept of exergy, previous theses in the subject are studied, mainly

two reports written by Göran Wall. (Wall 1986)

3.4 Definition of Exergy

To add a new perspective to other analysis methods investigating environmental

impacts and energy efficiency, this report is using the exergy concept. The exergy

analysis can give insight into the extent to which the quality levels of energy supply and

energy demand are matched.

To simplify the calculations including exergy in energy transformation there is a

method for converting energy to exergy. The exergy factor is defined

(1)

17

When the temperature of the energy is constant but differs from the surroundings, the

exergy factor can be defined as

(2)

where is absolute temperature in the object and the surrounding absolute

temperature.

Table 1. Exergy factors for some different energy sources (Molinari 2009)

A fuel which carries potential energy of some form, chemical, potential or other, has a

high exergy factor around 0.9. This is noticeable in table 1, as the fraction of useful

energy is high which does not depend on where the source derives from. When a fuel is

incinerated, heat is always submitted in the transformation of energy forms, which

means that exergy is destroyed since heat has a smaller fraction of useful energy than

the chemical energy content of the fuel. In other words, the exergy factor of the fuel is

reduced to the lower exergy factor of heat, due to the heat losses. When using any form

of fuel, waste, coal or other, for combustion, the exergy loss is always substantial.

Exergy efficiency describes how efficient the quality content in an energy carrier is used.

The efficiency is calculated as the exergy demand divided by actual exergy input. The

exergy input depends on how the exergy is generated, why primary exergy is of interest.

Efficiency for energy is calculated in the same way. The equations are:

(3)

(4)

How the quality in an energy carrier is used is most apparent in the conversion for

heating. Since it is clear in group 3 how the exergy and energy input is used, what is

Fuel Exergy

factor

Natural gas 0.9

Fuel oil 0.9

Mineral coal 0.9

Wooden pellets 0.9

District heating at 100°

C

0.21

Electricity 1

Heat at 20° C 0.05

18

used for heating and what is used for other purposes, one can determine its final

efficiency. Therefore efficiency for the operation phase are calculated and compared for

this group. This is not done for the two previous groups, since the data does not

explicitly state if some of the energy is used for heating.

3.4.1 The exergy content of electricity

Since electricity is an energy carrier of highest quality and all of the electric energy can

be used for useful work, the exergy factor for electricity is 1. Electricity is not a primary

energy source, but must be produced using some type of primary energy and then

transform it to electricity through different types of processes. To receive a certain

amount of electricity, a higher amount of primary energy is required as input. In the

same way the exergy amount will diminish as energy conversion takes place. This

amount of exergy depends on how the electricity is produced. In this report electricity

production on the margin is presumed and therefore coal is the primary energy source.

Further the electricity required for extracting and processing material is presumed to

derive from a coal condense plant with an efficiency of 40%. (Dodoo 2011) The

primary energy required to generate electricity can be calculated with the following

equation:

(5)

The reverse process, when observing how much energy that can be generated from a

given amount of primary energy, a primary factor can be calculated as

(6)

For example, if 100 kWh of electricity is needed to produce required building materials,

this means that 250 kWh of coal has been used. The exergy is calculated with the

exergy factor for coal found in table 1.

Figure 5. An example of energy and exergy flow when generating electricity.

This also implies that the primary factor for electricity on the margin produced this way

is 2.5 using equation 6.

100 kWh exergy

• 100 kWh electricity

η=0.4

• Coal power plant

225 kWh exergy

• 250 kWh coal

19

4. Data The examined buildings are two recent projects, currently in the phase of planning, led

by the constructor Järntorget. The two projects are to be built in the surrounding area of

Uppsala. One is a concrete frame residential building and the other is a wooden frame

residential building. The concrete frame building is a building with wooden facade, 56

apartments and net floor area of 6026.0 m². The wooden frame building has plastered

facade, 22 apartments and net floor area of 1592 m². Storage and stair wells are included

for the both concepts. See appendix C for building layout.

In the concrete frame building a combination of prefabricated concrete and in situ

concrete slabs will be used. The basement floor will be in situ slabs as well as 20 cm of

the course of logs. The remaining walls and 5 cm course of logs will be prefabricated.

This means that the remaining walls are not made of solid concrete. The building’s

insulation will contain of mineral wool and inside the walls there will be supporting

pillars of steel. (Johansson 2012) An estimation of the joist material is that 10 % is of

steel and 90 % is of insulation. Insulation in the roof is peat but is treated as mineral

wool in this report, due to lack of data concerning peat as an insulator. Mineral wool is a

more common insulation material, which makes the generalization reasonable

(Swedisol 2012).

The amounts of wood, work and transport necessary for the wooden facade at the

concrete frame building are being excluded, as there was no access to that data. This

differs from the wooden frame concept, but is taken into account in the Result and

Discussion part.

In the wooden frame building, Järntorget will use their standard construction system for

wooden frame buildings. (Johnsson 2012) This construction system implies using

modular elements and the foundation will consist of 1.5 cm oak board laid on a 16 cm

concrete slab foundation, 7 cm expanded polystyrene, and 15 cm crushed stone. The

external walls will consist of three layers, including 4.5 cm plaster-compatible mineral

wool panels, 4.5 x 12 cm lumber studs with mineral wool between the studs. (Dodoo

2011) The building will have a plastered facade which means that concrete will be used

for this purpose.

4.1 Data for Group 1: Extraction, Production and Transportation

In the construction of residential buildings several different materials are required. In

both wooden and concrete frame-buildings mostly the same kind of material is needed,

but in different amounts. When examining wood and concrete construction from an

exergy point of view, the materials for which the amount differs significantly between

the two construction types are especially worth looking in to. All presented values are

calculated for primary energy and exergy. As previously mentioned, the electricity is

20

assumed to be produced from a coal condensing power plant, and therefore the exergy

factor for coal is used when calculating primary exergy.

The following table states the different amounts of common material used and the

energy required to extract, produce, and transport each material.

Table 2. Amount in tonnes of air-dry materials and energy required in kWh/tonne.

(Johnsson 2012, Johansson 2012, Dodoo 2011)

Material Wood-

frame

Concrete-

frame

Coal Oil Fossil gas Biofuel Electricity

Concrete 298.33 4138 88.89 100.00 0.00 0.00 22.22

Plasterboard 119.07 34 0 791.67 0.00 0.00 161.11

Lumber 78.93 0 0 0.55 0.00 694.44 136.11

Particleboard 24.08 0 0 391.67 0.00 1394.44 419.44

Plywood 28.09 0 0 744.44 0.00 2650.00 483.33

Steel ore-

based 21.41 178 3916.67 855.56 1336.11 0.00 913.89

Insulation 28.09 128 2000.00 361.11 19.44 0.00 388.89

4.2 Data for Group 2: Construction Phase

The required energy for on-site assembling of the material from table 2 is presented in

table 3. Half of the energy required is assumed to consist of electricity and the other half

of fuel oil. (Dodoo 2011)

Table 3. Energy required in the construction phase in kWh/m2. (Dodoo 2011)

Data group 2 [kWh/m2] Wooden frame Concrete frame

Electricity 25 50

Fuel oil 25 50

Total 50 100

4.3 Data for Group 3: Operation Phase

The exergy demanding processes investigated in the operation phase are ventilation,

lighting, production of domestic hot water, and heating. In turn, the heating demand

depends on the features of the building, such as window size and position, U values for

the materials, and heat gains. The choice of heating system will also have an impact on

the total exergy consumption. All the values used for calculation in the operation phase

can be seen in Appendix D, and print screens from the modeling tool Annex 49 can be

seen in Appendix B.

The values for lighting power, ventilation power, specific internal gains of equipment,

etc. used in the model are values concerning a passive house. These parameters are

21

summarized and treated as heat gains and heat demands in Annex 49. Thermal bridges

around doors, windows, corner of the walls and edge beams have been available for the

concrete frame building. By estimating plausible values according to scale from the

concrete frame building, values for the size of the thermal bridges in the wooden frame

building have been calculated. U and psi-value are estimated and adjusted to be the

same for windows, doors and thermal bridges in the both concepts as well as the

window frame fraction and total heat transmittance through the windows, thus to lower

their impact on the result. The specific U values for the walls in the two concepts are

still differing.

The input value for air exchange rate is general standard in Sweden. Both air exchange

rate and the heat exchanger efficiency value is adjusted to be the same for both

concepts. Thus, the impact of the ventilation device does not differ between the two

building concepts. (Svensk ventilation 2012) A calculation of the average temperature

for each month during one year is made, (table 4) and then used to calculate the monthly

heat demand in the building concepts. The hours during each month when the buildings

have a heat demand are thereafter summarized. Values for domestic hot water, lighting

and ventilation are constant during the whole year, while the heat demand varies.

Table 4. Average temperatures for each month over one year

Month Average

temp

Jan -4,65

Feb -6,42

Mar -2,46

Apr 2,30

May 7,87

Jun 12,59

Jul 15,48

Aug 14,08

Sept 10,32

Oct 6,14

Nov 0,96

Dec -2,67

The heat source is based on the fuel mix for district heat in Uppsala at present time,

shown in figure 1, section 2.3. A generalization is made, where it is estimated that 50 %

comes from waste and 50 % from peat. It results in an estimated primary factor at 0,85.

The electricity source for lighting and ventilation power is electricity on the margin.

The numbers of occupants in the different building projects are important to estimate, to

22

be able to calculate a plausible value for Internal gains of equipment. An average

number of occupants in a household is estimated to 1,96 which would lead to an

average of 0,02 occupants per square meter in the observed buildings. (Central Bureau

of Statistics, 2012)

4.3.1 Data for different time perspectives of district heating in Uppsala

A future fuel mix for district heating in Uppsala, shown in figure 2, section 2.3, are

estimated to origin from 50 % waste and 50 % bio mass, which gives a primary factor

around 0,33. To make the report valid for a future situation with a new fuel mix for the

district heat in Uppsala, a modeling with the future primary factor for the district heat

was made and compared to the situation of today.

23

5. Results The main results are presented as primary exergy and energy consumption per square

meter and year, with an estimated lifespan of 50 years for both concepts.

5.1 Results for Group 1: Extraction, Production, and Transportation

The total amount of primary energy used for group 1, when extracting, producing, and

transporting building material, can be calculated and transformed into numbers of

exergy by summarizing the different energy sources showed in table 2 and multiplying

them with corresponding exergy factor from table 1, section 3.4. This is done with the

Excel sheet, see Appendix A. In table 5, the total amount of required exergy is presented

without regarding the different sizes of the two buildings.

Table 5. Energy and primary exergy calculations for extraction, production, and

transport.

Result group 1

[MWh]

Wooden

frame energy

Wooden

frame exergy

Concrete

frame energy

Concrete

frame exergy

Sum coal 167 150 1321 1189

Sum fuel oil 183 165 639 575

Sum fossil gas 29,1 26,2 240 216

Sum bio mass 16,3 147 0 0

Sum

electricity

9,07 81,7 310 279

Total sum 404 570 2510 2259

Table 6. Energy and primary exergy calculations for extraction, production, and

transport per m2 and year.

Result group 1

[kWh/m2

and year]

Wooden

frame

energy

Wooden

frame exergy

Concrete

frame energy

Concrete

frame exergy

Sum coal 2.09 1.88 4.38 3.95

Sum fuel oil 2.30 2.07 2.12 1.91

Sum fossil gas 0.37 0.33 0.80 0.72

Sum bio mass 2.05 1.84 0.00 0.00

Sum electricity 1.14 1.03 1.03 0.93

Total sum 7.94 7.15 8.33 7.50

The values for the concrete buildings shown in table 5 are much higher since the

concrete building is approximately three times larger than the wooden building. To be

able to make a relevant comparison, the calculated result is generated per square meter

and year, as shown in table 6. The data in table 6 are made visible as a diagram in figure

24

8. The amount of exergy and energy deriving from different sources as well as a total of

exergy and energy are shown. This demonstrates that the concrete frame requires a

slightly higher level of exergy than the wooden frame. In the group 1 processes it also

shows that the concrete frame uses more coal and zero amount of bio mass, while the

wooden frame is lower on coal and higher in bio mass.

Figure 6. Primary exergy per m2 and year group 1.

5.2 Results for Group 2: Construction Phase

The amount of exergy and energy for the two different building projects are shown in

table 7 and in table 8 the data have been valuated per square meter and year for easier

comparison. During construction, the concrete frame requires twice as much exergy and

energy per m2 as the wooden frame.

Table 7. Prmary energy and exergy calculations for the construction phase.

Result group

2 [kWh]

Wooden

frame energy

Wooden

frame exergy

Concrete

frame energy

Concrete

frame exergy

Electricity 39800 35820 301300 271170

Fuel oil 39800 35820 301300 271170

Total sum 79600 71640 602600 542340

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

kWh

/m2

Energy source

Exergy wooden frame

Exergy concrete frame

25

Table 8. Primary energy and exergy calculations per m2 and year for the construction

phase.

Result group 2

[kWh/m2

and year]

Wooden frame energy

Wooden

frame exergy

Concrete

frame energy

Concrete

frame exergy

Electricity 0.5 0.45 1 0.9

Fuel oil 0.5 0.45 1 0.9

Total sum 1 0.9 2 1.8

The diagram in figure 9 shows how the primary exergy and energy is distributed for the

two energy sources, electricity and fuel oil, during the construction phase.

Figure 7. Primary exergy results per m2 and year for the construction phase.

5.3 Results for Group 3: Operation Phase

By running modeling tool Annex 49 with different monthly average temperatures, the

exergy and primary energy required during the operation phase is calculated. Both

buildings have a heating demand during January to April and November to December.

During rest of the year the exergy and energy demand derives from domestic heat water,

lighting and ventilation power.

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

2

Electricity Fuel oil Total

kWh

/m2

Energy source

Exergy wooden frame

Exergy concrete frame

26

Figure 8. Primary exergy consumption monthly for group 3.

As seen in figure 10, the concrete frame building requires a higher amount of primary

exergy than the wooden frame during the months with heat demand. During the rest of

the year the required exergy is equal for both concepts. Table 9 shows annual energy

and exergy use for these processes. Figure 11 shows the total use for both buildings per

year during the operation phase.

Table 9. Annual demand for processes in the operation phase in kWh/m2and year

[kWh/m2

and year]

Wood frame

energy

Wood frame

exergy

Concrete

frame energy

Concrete

frame

exergy

Heat 8,59 0,43 12,84 0,64

DHW 21,10 1,06 21,10 1,06

Ventilation 2,40 2,40 2,40 2,40

Lighting 12,40 12,40 12,40 12,40

Total 44,49 16,28 48,74 16,50

0

1

2

3

4

5

6

7

8

9

Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec

kWh

/m2

Month

Exergy wooden frame

Exergy concrete frame

27

Figure 11. Total primary exergy consumption annually for group 3.

Figure 12 shows the energy and exergy demand during the operation phase and the

primary energy and exergy required to meet the demand. It is clear that the exergy

demand is relatively low but a high amount of primary exergy is still consumed. This

leads to low exergy efficiency, presented in table 10.

Figure 12. Energy, exergy, and primary energy and exergy for both concepts.

By looking at figure 12 it can be seen that a relatively large part of the used primary

energy is supplied to and used within the buildings’ different processes. However, a

major part of the exergy in the primary energy is lost since the exergy demand is lower

0,00

10,00

20,00

30,00

40,00

50,00

60,00

Exergy

kwh

/m2

Exergy wooden frame

Exergy concrete frame

0,00

10,00

20,00

30,00

40,00

50,00

60,00

70,00

energy primary energy

exergy primary exergy

kWh

/m2

Wooden frame building

Concrete frame building

28

than the exergy input. As seen in figure 12, a large part of the energy demand consists

of heat, which has a low exergy factor, and the exergy input used consists mainly of fuel

with a high exergy factor. This leads to high energy efficiency, shown in table 10,

which does not show how efficient the use of exergy is. In fact, the exergy efficiency is

comparatively low.

Table 10. Energy and exergy efficiency in kWh/m2

Wooden frame Concrete frame

Energy efficiency 0,80 0,81

Exergy efficiency 0,30 0,29

5.3.1 Results for different time perspectives of district heating in Uppsala

The impact of the fuel mix of the district heating is shown in figure 13. By changing the

mix of the fuel, and replacing peat with biomass, the required exergy for both concrete

and wooden frame can be diminished.

Table 11. Total energy and exergy required for group 3, use of both district heat of

today and tomorrow.

Total kWh/m2

Wood (Exergy) Concrete

(Exergy)

Wood (Energy) Concrete

(Energy)

Today 53.58 56.69 55.60 59.84

Tomorrow 38.64 40.16 39.67 41.13

29

Figure 13. Primary exergy per year during the operation phase, using both district heat

today and expected district heating in the future.

5.4 Total Result

The total amount of primary exergy required for all included phases of the buildings’

lifecycles are calculated in table 12. This data is used to generate the diagram in figure

14.

Table 12. Required primary exergy through all groups.

Total prim exergy [kWh/m2

and year]

Wooden

frame

Concrete

frame

Extraction, production, and

transports

7.15 7.50

Construction phase 0,9 1.8

Operation phase 53.58 56.69

Total 61.63 65.99

The diagram in figure 14 shows how the required primary exergy for the different

groups are distributed over the total amount of required, where the operation phase has

the largest impact.

0,00

10,00

20,00

30,00

40,00

50,00

60,00

Exergy wooden frame Exergy concrete frame

kWh

/m2

Construction type

Today

Future

30

Figure 14. Total amount of required primary exergy for all included processes of the

buildings’ lifecycles.

0

10

20

30

40

50

60

70

Wooden frame Concrete frame

kWh

/m2

Construction type

Operation phase

Extraction, production, and transports

Construction phase

31

6. Sensitivity Analysis To estimate the results and identify key parts in the calculations, a sensitivity analysis is

made. As some parameters in the modeling part are uncertain it is important to

investigate different inputs and outcomes. In this chapter three possible scenarios are

evaluated; change of heating source, change of life span and change of window

position.

6.1 Change of life span

The parameters in Group 1 and 2 are affected by the life span of the buildings. This

report does not include the fact that the two different building concepts have

maintenance and renovation needs. A likely assumption is that the concrete frame

building has a longer life span than the wooden frame building. By running the Excel

sheet with a life span of 75 years for the concrete frame building and 50 years for the

wooden frame building, in group 1 the required exergy and energy for the concrete

concept decreases below that of the wooden. This is shown in figure 15.

Figure 15. Primary exergy consumption for group 1, with a life span of 50 years for the

wooden frame building and 75 years for the concrete frame building.

Even though the required exergy for the wooden frame in group 1 exceeds the one for

the concrete frame, this is not the case for the total amount of required exergy. Since

group 1 has a limited effect on the total primary exergy consumption, the concrete

frame still has the highest consumption in total as seen in figure 16. The required exergy

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

kWh

/m2

Energy source

Exergy wooden frame

Exergy concrete frame

32

for the concrete frame has diminished to a more equal level, but not beyond that of the

wooden.

Figure 16. Total amount of required primary exergy, with a lifespan of 50 years for the

wooden frame and 75 years for the concrete frame.

6.2 Change of heating source

The examined projects can be seen as models for Järntorgets planned project in the

sustainable district Östra Sala backe in Uppsala. Therefore an evaluation of the required

heat for the buildings using the fuel mix of the district heat in Uppsala has been done for

group 3. To investigate how the exergy consumption changes when using other heating

sources, Annex 49 has been modeled using electric boiler as main source. The result,

seen in figure 17, shows a great increase in required primary exergy. This is because the

heating source consists only of electricity; with an exergy factor 1.The relation between

the two building concepts does not change.

0

10

20

30

40

50

60

70

Wooden frame Concrete frame

kWh

/m2

Construction type

Operation phase

Extraction, production, and transports

Construction phase

33

Figure 17. Amount of required primary exergy for both concepts, showing both usage of

district heating and electric boiler as heating source.

6.3 Change of window position

The position of the building and the position and amount of windows affect the solar

insolation through the window glass. The solar heat gain is largest in the south and east-

west direction. When changing the position of the windows in the buildings so that a

large amount of the window area is directed in the north direction, the solar heat gain

will decrease. This means that the heat demand increases which leads to larger exergy

and energy consumption. A calculation of this has been made and the result shows that

the demand increases with approximately 1% during those months heating is required.

0,00

20,00

40,00

60,00

80,00

100,00

120,00

140,00

Exergy wooden frame Exergy concrete frame

Kw

h/m

2

District heating

Electric boiler

34

7. Discussion It is important to emphasize that the comparison implemented in this report is between

two different building projects, not between general wooden and concrete frames. The

results in this report are therefore not necessarily valid for the general case.

In group 1 it can be observed that it is an essential difference in usage of energy sources

when producing construction material for the different concepts. When extracting,

producing and transporting material for a concrete frame there is no usage of bio mass

as an energy source, but the usage of coal as an energy source is twice as high as for the

wooden frame. Since coal, and other fossil fuels, has a higher primary energy factor

than bio mass, the total exergy consumption will be higher. This is because the concrete

frame does not use material deriving from wood and such.

By modifying the life span of the concrete frame building to be longer than that of the

wooden frame, it can be shown that the annual exergy demand for the concrete building

decreases immensely for group 1. This does not impact the total exergy consumption

considerably, since it is mostly the activities in group 3 that effect the total

consumption. Though, if a concrete frame building were to have a longer life span than

a wooden frame building, which is a likely scenario, the total difference in the exergy

demand of the two concepts would fall to a similar level. A building’s life span is an

important factor when investigating different building concepts, especially when aiming

towards creating sustainable city districts. By prolonging the life time of a building,

wooden or concrete frame, the exergy consumption is diminished.

Even though the required exergy for the construction of the concrete frame is twice as

large as for the wooden frame, the amount of required exergy in group 2 is the most

negligible one when summarizing the three groups.

It is during the operation phase, group 3, that the largest amount of required exergy

occurs. It implies that the heating of a building requires the highest amount of exergy

during a building’s life cycle. As the exergy efficiency shows, the exergy losses are

significantly larger than the energy losses. This is a good example of the value of an

exergy approach, instead of simply energy, when heating is concerned. The energy

efficiency does not reveal the losses of quality in energy.

Therefore, a low-exergy option is especially significant when it comes to choice of

heating system. The exergy consumption can be lowered if using a source for heating

that does not involve a large change of temperature where the exergy is destroyed. The

best way to achieve this is by using already heated elements that is a byproduct from

other processes, for example waste heat from industries. When going from waste heat to

indoor heat the exergy loss is at a minimum. Compared to the use of electricity for

heating, where the exergy factor (amount of useful energy) would fall from 1 to about

0.05 in the conversion, the losses are substantial. Using district heat for a building’s

heating demand poses a good option compared to other heat sources, such as an electric

35

boiler, since district heat have an exergy factor of 0,21. Though, it is important to

incorporate how the district heat is generated, realizing that when looking at primary

exergy, the district heat in fact derives from fuels with higher exergy factors. When

fuels are used, the exergy losses are generally large.

Having an exergy approach does not only concern itself with how much energy is used

but also how the energy is used, focusing on the quality of the energy. The amount of

energy used is still an important issue for sustainability, but using the right type of

energy for the right purpose is also at the heart of energy efficiency. In an exergy

analysis it is important that both fossil and renewable energy sources are used

efficiently. By striving for a minimum of diminishing exergy value at each step in

energy demanding processes, the losses will be kept low.

It can be established from the sensitivity analysis that choice of heating system has a

great impact on the total level of required exergy within the buildings. When changing

position of the windows, a minor change in heating demand occurs, independent of

building concept. Consequently, this factor is not the most important one to consider

when designing and constructing a building concept.

7.1 Sources of Error

Beyond the aspects discussed in the sensitivity analysis there are some factors in the

report that are uncertain and may affect the outcome.

In a life cycle perspective, Group 2, the construction phase, is a fairly negligible part.

This part can though be modified by changing the usage of construction materials, but

since the parameters does not have a major effect on the total exergy summation this

will not be examined in this report. As mentioned above, the material for inner- and

load bearing walls will be excluded for both projects. Excluding this will implicate a

lower amount of material than for constructing an actual building, but this is not

substantial when calculating the energy demand for the different buildings during the

operation phase in Group 3.

Since Group 3, the operation phase, has the largest impact on the total exergy

consumption, the inputs and results in this phase are the most considerable.

The amount and directions of doors and windows will have an impact on how large the

heating demand of the building is. To eliminate its impacts the same kind of windows

are used in the model. The amount of windows per square meter has been evaluated and

is equal for the both projects. The modeling is also performed using the same kind of

thermal bridges, but in reality the thermal bridges are adjusted after the specific concept

and can differ. When investigating the exergy demand for each month, the buildings’

varying heating demands are clearly to be seen. Though, since an average value for a

complete day’s temperature is used as input, those hours with low temperature are

36

therefore not visible in the calculations. This simplification means that some of the

actual heating demand will be excluded.

The modeling tool Annex 49 is adjusted to calculate heating demand for detached

houses. The general input values listed in the report above are not estimated from the

building projects led by Järntorget, but are standard values. They are though reshaped to

fit the investigated projects. In the model Annex 49, the parameter for internal gains of

equipment are valued as free energy gain. The parameter is estimated energy generated

from household appliances and other electrical devices; appliances that also need

energy. However, this is negligible when the comparison between the both building

concepts is made, since the error will have equal effect on both concepts.

The results for the different amount of materials are affected by the fact that wood

required for the wooden panels at the concrete frame building are excluded. Addition of

an estimated amount of wood to the material of the concrete frame building will just

higher the total effect.

The risk of fire, damage by damp or other unfortunate mishaps have not been taken into

account and an examination how this could impact the different concepts and therefore

the final results has not been done. When not including the demolition phase of the

buildings, the reusability of the different building materials is excluded. Both concrete

and wood can be reused in different forms, for example as filling and new building

materials, and in doing so the total use of primary exergy is diminished. Difference

between renewable and not renewable resources has not been made.

37

8. Conclusions An exergy analysis is a useful complement to consider whether energy is used in the

most efficient way. During the life cycle of a building, this is most noticeable when

considering heating system in the operation phase. From a life cycle perspective and

exergy point of view, considering all considered phases, the wooden frame building is

to prefer before concrete frame building.

As previously mentioned, the results for the examined buildings do not necessarily

represent a general building. If making different choices when it comes to materials and

design, results differing from this report are possible. However, the report concludes

that the property of used materials and a building’s features are of importance when

looking at a buildings exergy and energy demand.

Since group 1 and 2 are “one-time costs”, the life span of the building has large effect

on the outcome of the exergy demand in these phases. It is therefore important, from a

sustainable point of view, to construct buildings with long life span and low renovation

needs. This refers to both concepts, and is especially important when aiming towards

sustainable city districts, such as Östra Sala backe.

It is during the operation phase, especially when heating is required, the exergy

consumption is highest. As heat is of low exergy, a low exergy source should be used

for that purpose, to minimize exergy losses in the energy conversion. When using high

exergy sources, like electricity and such, for indoor heating, the exergy loss is

substantial. To secure efficient use of energy, high quality energy sources as electricity

should be used for purposes where no other alternatives are available, thus concluding

that for heating other options are present.

38

References Annex49 (2012-05-03)

http://www.annex49.com/background.html

Betongbanken 2010a: Sammanfattning (2012-04-27)

http://www.betongbanken.com/index.aspx?s=2453

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http://www.betongbanken.com/index.aspx?s=4339

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http://www.betongbanken.com/index.aspx?s=2649

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http://www.betongbanken.com/index.aspx?s=4333

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http://www.betongbanken.com/index.aspx?s=4325

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byggregler/BBR/

De Meester, B., Dewulf, J., Verbekea, S., Janssensb, S.,Van Langenhovea,H., 2008:

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et%20i%20siffror%202011.pdf

Swedish Energy Agency 2012b (2012-05-07)

http://energimyndigheten.se/Global/F%C3%B6retag/Milj%C3%B6v%C3%A4rderin

g/Underlagsrapport%20CO2%20vardering%20av%20energianvandning.pdf

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39

Gillberg, Björn, Fagerlund, Göran, Jönsson, Åsa, Tillman, Anne-Marie, 1999: Betong

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40

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41

Appendix A

42

43

Appendix B

44

45

Appendix C

Wooden frame

Concrete frame

46

Appendix D This appendix consists of the inputs used for group 3, calculated in Annex 49.

Wooden frame

Volume inside [m3]: 3980

Net floor area [m2]: 1592

Indoor air temperature [oC]: 21

Exterior air temperature [oC]: Varying

Area

[m2]

U value

[W/m2K]

Exterior wall: North: 150 0,21

South: 150 0,21

East: 234,35 0,21

West: 234,35 0,21

Window: North: 49,2 0,9

South: 49,8 0,9

East: 30,6 0,9

West: 25,7 0,9

Door: 8,8 1

Thermal bridges: Roof: 384,2 0,08

Ground: 384,2 0,1

Edge beam: 50,46 0,46

Corner of

wall:

29,58 0,16

Wall/Attic: 50,46 0,16

Window N: 124,48 0,09

Window S: 117,53 0,09

Window E: 55,5 0,09

Window W: 77,42 0,09

Door: 20,24 0,09

Air exchange rate [ach/h]: 0,5

Heat exchanger efficiency: 0,7

Window frame fraction: 0

Solar insolation [W/m2]

: South: 12

North: 6

East, west: 10

47

Total transmittance: 0,46

Number of occupants: 31,84

Specific internal gains of equipment

[W/m2]:

3,53

Specific lighting power [W]: 1,41

Specific ventilation power [W]: 0,217

Concrete frame

Volume inside [m3]: 15000

Net floor area [m2]: 6026

Indoor air temperature [oC]: 21

Exterior air temperature [oC]: Varying

Area

[m2]

U value

[W/m2K]

Exterior wall: North: 616 0,15

South: 826 0,15

East: 589 0,15

West: 888 0,15

Window: North: 190,3 0,9

South: 188 0,9

East: 254,4 0,9

West: 428 0,9

Door: 50 1,1

Thermal bridges: Roof: 842 0,08

Ground: 842 0,1

Edge beam: 174 0,46

Corner of

wall:

102 0,16

Wall/Attic: 174 0,16

Window N: 481,8 0,09

Window S: 644,6 0,09

Window E: 443,3 0,09

Window W: 923 0,09

Door: 115 0,09

Air exchange rate [ach/h]: 0,5

Heat exchanger efficiency: 0,7

Window frame fraction: 0,2

48

Solar insolation [W/m2]

: South: 12

North: 6

East, west: 10

Total transmittance: 0,46

Number of occupants: 120,42

Specific internal gains of equipment

[W/m2]:

3,53

Specific lighting power [W]: 1,41

Specific ventilation power [W]: 0,217