FOUNDATION DESIGN

(XEPS). Other materials, such as closed-cell ure-

thane, lightweight clinker, or wood chips, may

be used as insulators. Extruded polystyrene is

usually recommended in this country when

the insulation is to be buried. Its closed-cell

Existing Foundation

design inhibits moisture absorption, thus

enabling its thermal resistance to remain

Existing Foundation

high. Expanded polystyrene may be used

if precautions are taken to limit its expo-

sure to moisture.

FOUNDATION DESIGN

At the time of the weather station's

New Foundation

design, there were no publications avail-

able in this country to assist in an SIF

Ground Insulation

design. The designers resorted to using

the Norwegian Building Research Insti-

tute's (NBI 1986) charts, graphs, and

6 ft

28 ft

building details as a guide to assist in the

35.67 ft

design. It was found, however, that the

NBI publications addressed climates

a. Foundation plan.

only as severe as 4500 F-days. NBI's fig-

2 in. Extruded

4 in. Extruded

Polystyrene

Insulation

b. Foundation cross section.

8 Mil Polyethylene

5% Slope Finished Grade

1.5 ft

0.67 ft

6 ft

1 ft

NFS Drainage Layer

Figure 4. Foundation plan and

Native Soil

cross section.

ures were projected out to meet the conditions

The wall and ground insulations are 4-in.-thick

expected at Galena by using a simple least-

XEPS. It was determined that the ground insula-

squares regression analysis.

tion had to extend 48 in. along the side of the

The final foundation plan is shown in Figure

building and 72 in. at the corners. For ease of con-

4a and the cross section in Figure 4b. The bottom

struction and added safety, all of the ground insu-

of the footing is approximately 20 in. below

lation was installed out 72 in. from the building.

grade. The insulation chosen was an extruded

Design calculations required that the floor insula-

polystyrene with a density of 2.0 pcf, a vertical

tion be 2 in. thick throughout the structure, except

compressive strength of 30 psi, a thermal resistiv-

for a 3-ft strip along the outer wall that required a

ity (R-value) of 4.9 ft2-hr-F/Btu-in., and a ther-

4-in.-thick layer. However, the floor was con-

mal conductivity (k-value) of 0.204 Btu/hr-in.-F.

structed using only 2 in. of insulation throughout.

4