=+5-28.

A 24 × 40 ft (7.3 × 12.2 m) building has a full basement with uninsulated walls extending 5 ft

(1.5 m) below grade. The insides of the walls are finished with R-8 (R-0.7) insulation, a thin vapor barrier, and sin, (12.7 mm) gypsum board. Estimate an overall heat-transfer coefficient for the walls.