The exterior wall of a building consists of 100 mm thick face brick (k = 0.9 Wmí1 Kí1 ), 40 mm thick polystyrene insulating board (k = 0.036 Wmí1 Kí1 ), 125 mm thick concrete block (k = 1.8 Wmí1 Kí1 )...

The exterior wall of a building consists of 100 mm thick face brick (k = 0.9 Wmí1 Kí1 ), 40 mm thick polystyrene insulating board (k = 0.036 Wmí1 Kí1 ), 125 mm thick concrete block (k = 1.8 Wmí1 Kí1 ) and 15 mm thick interior gypsum board (k = 0.18 Wmí1 Kí1 ). The inside and outside convective heat transfer coefficients are 6.5 Wmí2 Kí1 and 22.5 Wmí2 Kí1 respectively. The outside air temperature is í5°C and the inside air temperature is 20°C. The wall is 3 m high and 15 m long. Calculate (i) the rate of heat loss through the wall, and (ii) the temperatures of the interior and exterior surfaces of the wall.