A 12-m-long and 5-m-high wall is constructed of two
layers of 1-cm-thick sheetrock (k 0.17 W/m · °C) spaced
12 cm by wood studs (k 0.11 W/m · °C) whose cross section
is 12 cm
5 cm. The studs are placed vertically 60 cm apart,
and the space between them is filled with fiberglass insulation
(k 0.034 W/m · °C). The house is maintained at 20°C and the
ambient temperature outside is 5°C. Taking the heat transfer
coefficients at the inner and outer surfaces of the house to be
8.3 and 34 W/m2 · °C, respectively, determine (a) the thermal
resistance of the wall considering a representative section of it
and (b) the rate of heat transfer through the wall