A building has a 9 ft deep basement (foundation) wall that is 160 ft long. The wall has no windows. On average, 8 ft of the wall is below grade (underground). Assume an outside air temperature of 10°F, an inside temperature of 70°F, and an average ground temperature of 45°F.
a. Determine the rate of heat loss through the wall below grade if it is uninsulated.
b. Determine the rate of heat loss through the wall below grade if it is insulated with an R-value of about 12 hr · °F · ft²/Btu.