Book - School of Science and Technology

Solar heat gains 87Office block corridor–fire escapeWindows 2.5 m x 3.5 mHall(10 m high inside)30 m20 mFoyerFigure 3.13 Heat gain exampleFrom examination of Table 3.6, it is clear that the south-west glass will be subject to thegreatest heat gain in the middle of the afternoon. To estimate the peak heat gain addtogether the peak SW gain with that of the corresponding NE gain. Not surprisingly itoccurs in June at 14.30 sun time (15.30 BST). This time and date will therefore be the basisfor the calculation which follows.GlazingSolar gainArea:SW exposure ˆ 5(2:5 3:5) ˆ 44 m 2NE exposure ˆ 5(2:5 3:5) ˆ 44 m 2From Table 3.6, the unit cooling loads are:SW glazing ˆ 309 W/m 2NE glazing ˆ 150 W/m 2From Table 3.7, taking the building mass to be `heavy' with slow response:Blind shade factor ˆ 0:94Air temperature control factor ˆ 0:89Thus, the cooling load arising from solar radiation:SW glazing ˆ (44 309 0:94 0:89) ˆ 11 374 WAdd 10% for radiation from pavement ˆ 1137 WNE glazing ˆ (44 150 0:94 0:89) ˆ 5522 W ˆ 18 kW