certain cases, the absorbed heat ¯ux of 200 W/m2 was used
for comparison. Thus, the absorbed heat ¯ux is only a small
portion of the solar irradiation, which can actually reach
700 W/m2. The heat transfer coef®cient of the walls and the
roof was chosen as 0.8 W/m2 K, assuming a well-insulated
house. Larger values of the coef®cient, up to 2.0 W/m2 K,
have been tried, as well. Changes in the heat-transfer
coef®cient of the walls did not lead to noticeable changes
in the results. However, since the roof is quite hot, an
increase in U would affect the temperature of the ceiling.