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
16 feet to building centerline
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
16 feet to building centerline
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
16 feet to building centerline
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
RATIO = .88 RATIO = .93
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
RATIO = .80 RATIO = .79
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
RATIO = .87 RATIO = .88
f-f-f-l-
f-f-I-
L-J L-J
4' WALL INSULATION 4' WALL INSULATION
SILT NO LATENT HEAT SILT NO SNOW
RATIO = .88 RATIO = 1.22
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
RATIO = .93 RATIO = 1.01
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
RATIO = 1.91 RATIO = 2.03
l-I-
I--l- I-
l-
t- l-
t- l-I-
8'~L + L-.J
SLAB INSUL. 8' WALL INSUL.
GRAVEL GRAVEL
RATIO = 1.66 RATIO = 1.78
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
RATIO = .82 RATIO = .84
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
8' WALL INSULATION 4' WALL INSULATION
SILT SILT
RATIO = .75 RATIO = .86
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
RATIO = 1.33 RATIO = 1.51
f-
8'~L + L-J
SLAB INSUL. 8' WALL INSULATION
GRAVEL GRAVEL
RATIO = 1.08 RATIO = 1.15
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
RATIO = .98 RATIO = .87
, I' WALL + "I' HORIZ. END OF SLAB +
SKIRT INSUL. "I' SLAB INSUL.
SILT SILT
RATIO = .86 RATIO = .82
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
RATIO = .81 RATIO = .79
" ... l-I- l-I- l-
II
4' WALL, l' DOWN + 4' WALL, l' DOWN + 4' SKIRT HORIZ. INSUL. 8' HORIZ. SKIRT INSUL.
SILT SILT
RATIO = .76 RATIO = .74
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
RATIO = 1.98 RATIO = 1.68
"'! 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
RATIO = .89 RATIO = .83
£ :} 4' WALL + 4' WALL INSULATION 4' SKIRT INSUL.
SILT SILT
RATIO = .80 RATIO = .78
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
RATIO = .78 RATIO = .75
~ 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
RATIO = 1.85 RATIO = 1.53
"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