heat loss factors for insulated building … b3 papers/035.pdfbuilding foundations j.p. zarling w.a....

HEAT LOSS FACTORS FOR INSULATED

BUILDING FOUNDATIONS J.P. Zarling W.A. Braley

Non-steady-state fini te element analyses of the heat loss occurring fran basanent and

slab-on-grade constructions have been perfonned. The anntmt of rigid foam insulation was

varied on the perimeter of the walls and slab to detennine the effectiveness of various

insulation configurations. Annual heat losses per linear foot of wall or slab are reported

for weather conditions and soil types in both Anchorage and Fairbanks, Alaska.

Insulation of basement walls and floor slabs in roost Alaskan locations has becane the

standard design practice for new building construction. Yet no standards exist on the

amount of insulation or the method of placing the insulation for an econanically justified

energy conserving design. This report addresses a portion of this problem by evaluating the

transmission heat losses that occur through various basement wall and floor slab insulation

configurations. The data presented should assist the 'ui Iding designer and owner in

choosing the most effective means of using insulation for these types of building

construction. ASHRAE (1981) does provide a methodology for calculating steady-state heat

losses for basements and slab-on-grade construction. The technique does not account for

nonsteady heat flaw, snow cover or varying soil properties.

ANALYSIS

The heat loss analyses of the basement wall and floor slab insulation systems were performed

on a non-steady-state basis. Because of the complexity of the geanetry and the

nonhamgeneity of the materials, the heat transfer analyses were done using nmnerical

techniques programned for a digital computer. A non-steady-state, two-dimensional finite

element program (Wang 1979) has been inplemented on a university computer system. This

program uses triangular and/or quadrangular elements allowing the specification of thennal

conductivi ty, specific heat and latent heat of each element. The program accounts for

freezing and thawing by using an apparent specific heat. The apparent specific heat is

calculated as the sum of the frozen specific heat and the soil volumetric latent heat

465

divided by an assumed phase change teo:perature range. In fact, rmst fine grained soil.s

exhibi t scme subcool ing and a release of latent heat over a tenperature range as the

unfrozen water content freezes.

The apparent specific heat approach to solving the thennal regime in a soil with

freezing/thawing using the finite element method can lead to stability problems.

Osci llation of nodal teo:peratures at the freeze/thaw front was typical of the stabil ity

problems experienced when using large elements. Numerous runs were made using the Wang

program in which element and time-step sizes were varied to investigate their effect on

stability. Element and time-step sizes were reduced to minimize this effect. When

cct:rparison runs of the annual heat loss were made using a fine mesh and a three-day time

step to a coarse mesh wi th a 14-day time step, results differed by 4% for a 20% rooisture

content soil and 3.5% for an 8% moisture content soil.

Boundary t6Iperatures or heat fluxes nust be specified, but because the model is

non-steady-state, these boundary condi tions can be varied wi th time. The lIDdel allows

convective heat transfer at any of the bounding surfaces, in which case the air temperature

rather than surface temperature is specified. Heat fluxes occurring across the isothenmal

botmdaries are calculated. These heat fluxes are integrated wi th respect to time to arrive

at annual heat loss through the basement wall and/or floor slab. The initial conditions for

the soi I tenperature were set equal to those previously calculated for a noninsulated

foundation system. The progrmn was allowed to run through two annual cycles to establish

equilibriun before integration of the heat fluxes 'Was initiated during the third annual

cycle.

Foundation Systems

The thern:al energy losses for four different foundation systems have been studied. The

characteristics of these four foundations, shawn in Figure 1, are outlined as follows,

1. Full Basement

2.

3.

8-inch masonry block wall extending to a depth of 8 feet below the

groWld surface

6-inch thick concrete floor slab

8-inch thick, 24-inch wide concrete footing

16 feet to building centerline

Monolithic Slab-on-Grade

6-inch-thick concrete slab with I-foot-thick by 18-inch-wide

perimeter concrete footing


Slab with Grade Berun

6-inch-thick concrete slab

8-inch masonry block grade beam extending 4 feet in depth

8-inch thick, 24-inch-wide concrete footing

466

1 j

1 ·1

I I 1 1 , 1 I


4. Daylight Basement

8-inch masonry block wall extending 4 feet below ground surface

6-inch-thick concrete slab

B-inch-thidk, 24-inch-wide concrete footing


Thermal Property Data

The following list of thermal properties and their values were used in the finite

element analysis.

Property

Soil (sandy-silt or silt)

Dry densi ty, Ib/ft3

Moisture content, % Frozen thenmal conductivity,

Btu/h·ft·F

Thawed thermal conductivity,

Btu/h·ft·F

Frozen specific heat, Btu/ft3'F 3 Thawed specific heat, Btu/ft ·F

Volumetric latent heat, Btu/ft 3

Gravel

Dry density, Ib/ft3

Moisture content, % Frozen thenmal conductivity,

Btu/h' ft·F

Thawed thenmal conductivity,

Btu/h· ft·F 3 Frozen specific heat, Btu/ft .F

Thawed specific heat, Btu/ ft 3'F

Volumetric latent heat, Btu/ft3

Insulation (extruded rigid polystyrene)

Density, Ib/ft3

Thermal conductivity, Btu/h.ft.F

Specific heat, Btu/ft3'F

I..ocation

Anchorage

124

10

1.15

1.0

22

33.2

1,750

135

7

2.2

1.9

27.6

32.4

1,300

467

2

0.015

0.52

and Value

Fairbanks

104

8

0.55

0.55

22

26

1,250

135

5

1.6

1.6

26

30

950

Concrete

Densi ty, Ib/ft3

Thermal conductivity, Btu/h·ft·F

Specific heat, Btu/ft3

.F

Masonry Block

Snow

Thermal conductivity, Btu/h'ft'F

Specific heat, Btu/ft3

.F

Density, Ib/ft3

Thermal conductivity, Btu/h·ft·F

Boundary Conditions

140

1.0

28.0

0.53

12.8

15

0.1

Zero heat flux normal to the vertical boundaries was specified. The ground, slab, wall

and floor surfaces were chosen as convective boundaries. A surface conductance of 1.08 2 Btu/h.ft .F (R = 0.93) was used for the slab and floor surfaces :md a value of 1.47 2 Btu/h.ft .F (R = 0.68) was used for the wall surface. The ground surface conductance was

seasonally varied to include the thermal resistance of the snow cover. During periods

assumed to have no snow cover (Apri I 15 to October 15), a surface conductance of 4.0 2 Btu/h.ft 'F was used. During the remainder of the year, we assumed snow cover was two-feet

deep for Fairbanks and one-foot deep for Anchorage. Surface conductance of 0.05 (R = 20)

and 0.10 (R = 10) Btu/h'ft2 'F, respectively, were used to si1llllate the camined snow and

surface resistance. Because of the wanning effect of the building, the snOW' cover was

varied in depth frem zero at the building wall to full depth one foot away. Air

tenperatures adjacent to the interior wall, slab and floor surfaces were set at 70F.

Outdoor air temperatures were assumed to vary according to a sinusoidal function where the

anplitude, A, and mean annual tenperature, T, were taken fran Hartman and Johnson (1969). o m

The express i on used was

T=T -A cos m 0

where

Tm = 26F, Fairbanks

T = 35°F, Anchorage m A = 36F, Fairbanks

o Ao = 230 F, Anchorage

t :::;;: time, daysz

" = seasonal Ig

The deep ground tenperature for each site was specified as the bottan horizontal

isothermal boundary condition. T = 39°F for Anchorage, and T = 34°F for Fairbanks.

468

•

RESULTS

The results presented in this paper should be viewed as the upper and lower bounds to the

heat loss from slab and basement structures. In actual situations, an absence of snow cover

or an lIDdisturbed snow cover of hvo feet for Fairbanks or one foot for Anchorage for an

entire winter is doubtful. Therefore, the ureal" heat loss frem either a slab or basement

should be bounded by the values reported for the snow and no-snow cases.

The base case used in the non-steady-state basement analysis was the uninsulated

basement with a snow cover and silty soil conditions. Figures 2 through 7 show the effect

of soil type and insulation treatment on the ratio of annual heat loss to base-case annual

heat loss for Fairbanks. These results indicate a doubling of heat loss from the base case

(when gravel replaces the si I t as the surrOl.mding soi 1; gravel has a higher thermal

conductivity) and a 23% reduction of heat loss when two inches of insulation are placed on

the entire wall and below the floor slab. Leaving the concrete footing uninsulated allows a

thermal bridge for a higher heat loss from this area. Annual heat loss is mainly influenced

by snow cover, soil thennal conductivity, insulation, and, to a lesser degree, soil latent

heat. Similar results are shown in Figures 8 and 9 for basement located in Anchorage.

Finally, a summary presentation of annual heat loss for the non-steady-state basement case

is presented in Figures 10 and 11. Annual heat losses per foot of wall perimeter are shown

for Anchorage and Fairbanks as a function of soil type and insulation configuration. Silty

soils with extensive insulation have the lowest annual heat loss, as expected. However, the

cost effectiveness of the under-basement-slab insulation appears questionable due to the

I1flatness ll of the curve. Adding these insulating features to a full basement with insulated

walls may not be economically justified.

Figures 12 and 13 show the ratios of annual insulated heat loss to annual uninsulated

heat loss for various slab-on-grade insulation configurations in Anchorage and Fairbanks.

The results indicate a reduction in annual heat loss of about 12% for just perirreter

insulation placed around a slab to 40% to 50% for full insulation treatment. A summary of

these figures is presented in Figure 14.

Figures 15 through 22 show the ratios of annual heat loss from a slab with grade beam

and/or daylight basement foundation with varying insulation configurations, soil types, and

snow cover to the annual heat loss fran an uninsulated foundation with snow cover. These

results show that annual heat loss is reduced by 19% from the Uninsulated case by applying 4

feet of insulation to the grade beam. Adding 4 feet of insulation to the daylight basement

foundation wall reduces the heat loss by 20%. A .summary of these results is given in

Figures 23 and 24 in tenns of annual heat loss per foot of foundation perimeter.

Economic Analysis

Because of the wide variation in energy and construction costs in Alaska, no atterrpt has

been made in this report to perform a quantitative economic analysis of insulation systems

by region. However, we present a methodology for choosing the optinun insulation

configuration based on engineering econcmic principles. There are several approaches to

perfonning an engineering economic analysis on the optimum insulation thickness and

469

configuration. The approach presented here uses the capital recovery factor to annualize

the capital cost recovery factor to annualized capital cost of the project. The annualized

capital cost is then added to the annual energy cost to arrive at the total annual cost of

the structure. When this analysis is perfoltIled for each insulation configuration, a new

total annual cost is calculated. The optinrum econanic insulation configuration is the

configuration yielding the lowest annual cost.

The capital recovery factor is CRF = i/[1-(1 + i)-nl where n is the number of periods

or useful life of the project, and i is the market interest rate. Market interest rate is a

function of the investment activities in financial and business communities as reflected by

actual rates of interest. The market interest rate (or minimum attractive rate of return)

includes effects of both the earning and purchasing power of money as well as project risk.

Therefore, an increase in the rate of inflation or project risk usually results in an

increase in the market interest rate. Using the market interest rate places cash flows in

tenms of actual or out-of-pocket dollars at any time. The CRF is multiplied by the total

cost ($/ft2) of construction (material plus labor cost) to arrive at the annualized cost of

the wall. The annual energy cost is calculated by mul tiplying the present cost of energy

($/Btu) times the annual heat loss for the construction (Btu/ft 2.yr) divided by the heating

system seasonal efficiency. The annualized capital cost and annual energy cost are added

together to arrive at the total annual cost ($/ft2) per year. Figure 25 shows conceptually

the results of these calculations for typical insulated constructions.

As seen in the figure, small amounts of insulation yield a low annualized capital cost

through a high annual energy cost. IJarge ~unts of insulation yield opposite results. The

optimum insulation configuration is the low point on the total annual cost curve. It should

be noted that high discount rates, short life projects, and low fuel costs will shift the

minimum point toward small amounts of insulation. Opposite trends in these it~ will shift

the optimum to greater thicknesses. This simplified approach does not include such

variables as annual maintenance, inflating fuel costs, or salvage value of the building at

the end of its useful life.

ClN1lJSICN

Results of finite element thermal analyses have been presented for (1) full basement, (2)

slab on grade (3) slab on grade with grade beam, and (4) daylight basement. Varying amounts

of 2-inch-thick rigid foam insulation were placed on the different fotmdation systffi1B to

study the effect of insulation configuration on annual heat loss. Life-cycle costs of the

insulation systems were not investigated; therefore, the "optiIl1tIDll1 insulation system has not

been determined. However, the annual thennal losses we presented are required to conduct

the economic analysis.

OUr results show that snow cover has a significant effect on the annual heat loss fram

foundations. A two-foot-deep undisturbed snaw cover will reduce annual heat loss by up to

30% carpared to bare ground. Soi 1 thennal conductivi ty also has a great effect on the

annual heat loss. Sands and gravels (having a much higher thermal conductivity than silts)

cause the annual heat loss to increase by 110%. Full insulation on an 8-£00t basement wall

wi 11 reduce the annual heat loss by 20% wi th a snow cover and 30% wi thout a snow cover.

470

Insulating a basement wall with gravel fill without a snow cover leads to a 16% decrease in

armual heat loss. As expected, insulating the wall, footing and slab yields the largest

reduct ion in annual heat loss: 26% for snow-covered condi t ions and rr¥Jre than 32% for

bare-ground conditions.

For slab-an-grade construction, insulating the perimeter of the slab reduces the annual

heat loss by about 12%, Whereas insulating the perimeter and under the slab reduces the

annual heat loss by 50%. For the grade beam case in silt, insulating to the top of the

footing resul ts in a 19% reduction in heat loss. Rermving the snow cover increases the heat

loss by 30% for the uninsulated wall, and changing to a gravel soil doubles the heat loss.

Care should be exercised to prevent frost heave When insulating basement Vi/alls and

slab-on-grade construction. Although the isothenns shown in Figures 5 through 12 do not

indicate frost heave problems, periods of extremely cold weather (e.g., -50F for two weeks)

can cause the freezing isothenn to penetrate below the slab. Nonfrost susceptible materials

must be used to a depth greater than the maxim.m depth of freeze to prevent frost heave

damage.

ASHRAE handbook -1981 fundamentals, pp. 25.7-25.9. Atlanta: American Society of Heating,

Refrigerating and Air-Conditioning Engineers, Inc.

Boileau, G.G., and J.K. Latta. 1968. "Calculation of basement heat losses." Division of

Building Research, Ottawa, Canada. Tech. Paper No. 292, 9 pp.

Hartman, C.W, and P.R. Johnson. 1969. Environmental Atlas of Alaska. Institute of Water

Resources, University of Alaska, Fairbanks. 95 pp.

Holman, J.P. 1981. Heat Transfer. New York: McGraw-Hill.

Wang, F.S. 1979. "Mathematical rrodeling and cooputer sirrulation of insulation systems in

below grade applications. II Proceedings of ASHRAE/IDE Conference on Thennal Perfonnance

of the Exterior Envelopes of Buildings, Orlando, FL.

The authors gratefully acknowledge the technical suggestions and funding provided by the

Alaska Department of Transportation and Public Facilities, Research Section.

471

:!3 '"

FULL BASEMENT

~ SLAB 'ITH GRADE BEA,

DAY-LIGHT BASEMENT

L....JF'"'=~

~ SLAB ON GRADE

Figure 1. Characteristics of four foundation systems

l n t 5 _______ ~

r r r

r r r

4' HO~ SKIRT 4' WALL~' HORIZ. INSUL. AT SURFACE SKIRT INSUL. AT 4'

SILT SILT

RATIO = .90 RATIO = .85

r r t-

2' WALL~' HORIZ. L--...J

SKIRT INSUL. AT 2' 2' WALL INSUL.

SILT SILT


Figure 2. Fairbanks, ratio = heat 10ss/ uninsulated heat loss in silt

... ~ w

f-f-

f-f-f-f-

f-f-

L-J 8' WALL~' HORIZ.

8' WALL INSUL. SKIRT INSUL. AT 8'

SILT SILT


l-I-

L-J L-J

8' WALL INSUL. 8' WALL INSUL.

SILT NO' LATENT HEAT SILT NO SNOW

RATIO = .81 RATIO = 1.10

Figure 3. Fairbanks, ratio = heat loss/ uninsulated heat loss in silt

f-f-l-

f-

L-J L-J

4' WALL INSULATION 4' WALL INSULATION

SILTINSUL. R DOUBLED SILT


f-f-f-l-

f-f-I-

L-J L-J


SILT NO LATENT HEAT SILT NO SNOW


Figure 4. Fairbanks, ratio = heat 10ss1 uninsulated heat loss in silt

~ ..

I-- ~

I-- -;0-

I--I-- I--I--

I--

L-J L-J

NO INSULATION NO INSULATION

SILT NO SNOW GRAVEL

RATIO = 1.54 RATIO = 2.11

I--

I--I--I--

I--I--I--

L-J L-J

2' WALL INSUL. NO INSULATION

SILT SILT NO LATENT HEAT


I

Figure 5. Fairbanks, ratio ~ heat 10ss1 uninsulated heat loss in silt

~

I--f- I--

l-I-

~ l-I-

~ L-J L-.J

8' WALL INSUL. 4' WALL INSUL.

GRAVEL GRAVEL


l-I-

I--l- I-

l-

t- l-

t- l-I-

8'~L + L-.J

SLAB INSUL. 8' WALL INSUL.

GRAVEL GRAVEL


Figure 6. Fairbanks, r'atio = heat 10ss1 uninsulated heat loss in silt

... ~ ~

II- II-

If- ,f-f- f-f- f-l- f-l- f-l-

f-

L-J L-..J 6' WALL + 4' VERT. SKIRT INSUL. AT 8' 6' WALL INSULATION

SILT SILT


l-I-l-f-f-

L-J

6' WALL INSULATION

SILT INSUL. R DOUBLED

RATIO = .79

Figure 7. Fairbanks, ratio = heat loss/ uninsulated heat loss in silt

r-

r- r-r- r-r- r-r- r-

L-...J L-...J


SILT SILT


L.....J

8' WALL + SLAB INSULATION

SILT

RATIO = .72

Figure 8. Anchorage, ratio = heat loss/ uninsulated heat loss in silt

t; '"

f- f-f-f-f-f-

f-

L-J L-J

4' WALL INSULATION NO INSULATION

GRAVEL GRAVEL


f-

8'~L + L-J

SLAB INSUL. 8' WALL INSULATION

GRAVEL GRAVEL


Figure 9. Anchorage, ratio = heat 10ss1 uninsulated heat loss in silt

-80 t;: I

'" L580 >-"-::J 1-70 CD .. o ~.o

en ~60 --' I-

L:S 40 J:

--' :5 30 z z ""

------

LOCATION AND SOIL TYPE C FAIRBANKS GRAVEL

o ANCHORAGE GRAVEL

A ANCHORAGE SILTY-SAND

Q FAIRBANKS SILT

-----20 ! NO 2 fr. -t;T. 8;T. nil WALL+ WALL... WALL+

INSUL. ON ON ON WALL UNDER VERT. UNDER WALL WALL WALL (8 FT.) SLAB SKIRT SLAB+FOOT

INSULATION CONFIGURATION

Figure 10. Basement annual heat loss for various insulation configurations

a Of ,~~ ".lie; . ___ ._. ___ . ___ ._"_ .. _. ___ .~ ..

;::::90 LL I

'" L510 >-"-::> ~70 .. 0 -00 ~

en ~60 -' ... I-.., .., L5 ... 0 :I:

-' :§ 30 z z -<

20

~

NO INBlA..

fAIRBANKS SILT C NO SNOW COVER

o NO LATENT HEAT

• 4 FT. HOR!. SKIRT AT BOTTOM OF WALL INSUL.

2 FT. 4 FT. eFT. FlA.L ON ON ON WALL

WALL WALL WALL (8 FT.) INSULATION CONFIGURATION

WALL ... UNDER BLAB

Figure 11. Basement annual heat loss for various insulation configurations

v;x;xyooodC; .58

FULL + 2' HORIZ. SKIRT INSUL.

~C; .58

FULL INSULATION

WO<>OO<XlJ .74

END + SLAB INSUL .

~C; .72

END, FOOT, + 4' SLAB INSUL.

v;x;xyooodL/ .82

END + 2' HORIZ. SKIRT INSUL.

~ .87

END INSULATION

Figure 12. Fairbanks transient heat 10ss1 uninsulated heat loss

t; ~

wosxxxxJG .50

FULL + 2' HORIZ. SKIRT INSUL.

~G .51

FULL INSULATION

w<XXXXXlL/ .69

END + SLAB INSUL.

~G .72

END, FOOT, + 4' SLAB INSUL.

wosxxxxJL/ .84

END + 2' HORIZ. SKIRT INSUL.

~L_~ .89

END INSULATION - - ---- --- ---- --------

Figure 13. Anchorage transient heat loss/ uninsulated heat loss

t"I

40

~ 36 W >-"-::> ::c 30

~

o

26

'" gJ -' t- 20 .., w :I;

~ 16 ::> z z ..,

LOCATION AND SOIL TYPE D ANCHORAGE SANDY-SILT

o FAIRBANKS SILT

I • ' , , , , , 10 NO END END END END FULL FULL

INSUL. OF WlHORt. + FOOT INSUL. W/HORI. SLAB SKIRT SLAB 4' SLAB SKIRT

INSULATION CONFIGURATION

Figure 14. Slab-on-grade annual heat loss for various insulation configurations

... ~

'"

, , NO INSULATION END OF SLAB +

4' SLAB INSUL.

SILT NO SNOW SILT NO SNOW

RATIO = I.SO RATIO = 1.00

, 4' WALL INSULATION

SILT NO SNOW

RATIO = .95

---

Figure 15. Slab with grade beam. Fairbanks; ratio = heat loss/uninsulated heat loss in silt

, r-r-r-e..

END OF SLAB INSUL. 2' WALL INSUL.

SILT SILT


, I' WALL + "I' HORIZ. END OF SLAB +

SKIRT INSUL. "I' SLAB INSUL.

SILT SILT


Figure 16. Slab with grade beam. Fairbanks; ratio = heat loss/uninsulated heat loss in 8i1 t

I

I

!

.. ~

"'! ••

l-I-I-

U

4' WALL INSULATION 4' WALL + l' DOWN INSULATION

. SILT SILT


" ... l-I- l-I- l-

II

4' WALL, l' DOWN + 4' WALL, l' DOWN + 4' SKIRT HORIZ. INSUL. 8' HORIZ. SKIRT INSUL.

SILT SILT


Figure 17. Slab with grade beam, Fairbanks; ratio = heat loss/uninsulated heat loss in silt

, =-1 NO INSULATION END OF SLAB +

4' SLAB INSUL.

GRAVEL GRAVEL


"'! 4' WALL INSULATION

GRAVEL

RATIO = 1.74

Figure 18. Slab with grade beam. Fairbanks; ratio = heat loss/uninsulated heat loss in silt

, . " .... ... b._ 1ft _~_~ ... ~ .. __ ~

.... ~

! =;t 2' WALL INSULATION 2' WALL +

4' SKIRT INSUL.

SILT SILT


£ :} 4' WALL + 4' WALL INSULATION 4' SKIRT INSUL.

SILT SILT


Figure 19. Daylight basement, Fairbanks; ratio = heat lossluninsulated heat loss in si1 t

, 4' WALL + 4' WALL + 2' VERT.

SLAB INSUL. SKIRT INSUL.

SILT SILT


~ l-I-l-I-

1\

4' WALL, FOOT, + SLAB INSUL.

SILT

RATIO = .72

Figure 20. Daylight basement, Fairbanks; ratio = heat loss/uninsulated heat loss in silt

.. 00 N

! "I NO INSULATION 4' WALL INSULATION

SILT NO SNOW SILT NO SNOW

RATIO = 1.24 RATIO = .91

c

"I 4' WALL + SLAB INSUL.

SILT NO SNOW

RATIO = .87

---_._- ~ ~~-

Figure 21. Daylight basement, Fairbanks; ratio ~ heat loss/uninsulated heat loss in sil t

-

~1 "I NO INSULATION 4' WALL INSULATION

GRAVEL GRAVEL


"I 4' WALL +

SLAB INSUL.

GRAVEL

RATIO = 1.43

Figure 22. Daylight basement. Fairbanks; ratio = heat lossluninsulated heat loss in silt

. • .. ''''" . .'"" j

" w

50

>-'tOO "" -<: "-' :::: ... => >-'" .. ~ o -,. w w

:ho >--< ~26

-" -< => 2. z z

[J SILT

o SILT NO SNOW

J:.. SILT W/GRAVEL FILL

+ ALL GRAVEL

~ ~~ ~ 8 S

8 -El

-<lSi , , " t",

NO ENO 2'WALL I'WALL END+ "'WALL <I'WALL ",,"IIALL <I'WALL INSUL. SLAB of'SKIRT ",,'SLAB t'DO\lN I'DO\lN 1 'DOWN

""SKIRT a'SKIRT INSULATION CONFIGURATION

Figure 23_ Slab -with-grade-beam annual heat loss for various insulation configurations

76r---:-------__ --____ --~--__ --__ --__ --_, t 70 , <'<: ;306 r "-=> 6. >-'"

• 66 o

- 6. w w 0 .. -"

~ .. o "-' :r: -" 36 -<: => z 3. z

a FAI SILT

o fAI SILT NO SNOW

,b. FAJ GRAVEL

~~ ~ -<:

26 I NO 2', 2'WALL "'WALL '''WALL ""WALL "'WALL "'WALl.. INSUL WALL of'SKIRT ",,'SKIRT ,,'SLAB 2'VERT ,,'SLAB

SKIRT FOOT INSULATION CONFIGURATION

Figure 24. Daylight basement annual heat loss for various insulation confi gurati ons

ten o u ...J ...:: ;:) z z ...::

FUEL + INSULATION

FUEL

to THICKNESS OF INSULTATION

Figure 25. Typical curves of costs vs. insulation thickness

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