Thermal Environment in Houses in Lowland Terai, Nepal

In order to characterize the seasonal indoor thermal environment in the southern part of Nepal, meteorological observations were conducted in three residential buildings with different roof types. The results are summarized as follows:1) In the non-monsoon season, the temperature rose steeply after the sunrise and the diurnal range was greater than during the monsoon season. During the daytime on a clear day, the roof surface temperature differed according to the type of roofing material, which was confirmed to be the main cause of the indoor temperature difference. The daytime indoor temperature was the highest in rooms under a zinc-coated steel roof, and the nighttime indoor temperature was the highest in rooms under a concrete roof. These results confirmed that the indoor temperature was correlated with the thermal characteristics of the roofing material.2) In the monsoon season, the diurnal range in temperature was small under the influence of the seasonal rainfall and high humidity. During the daytime, the indoor temperature under the zinc-coated steel roof was high, while that under a tile roof was low because of the temperature difference between the two material types. Tile roofs are porous and retain water, and therefore their heat-suppressing effects are greater than those of zinc-coated steel roofs due to water and moisture retention. Zinc-coated steel roofs are thin and do not retain water. These results were observed more clearly on mostly clear days with occasional rain. It was also apparent that rainfall had a strong influence on indoor temperature.