Dr. Basudev Gautam, Tokyo, Japan - - -
Nepal has geographical variation ranging from 60m to 8848m. Its climate varies from sub-tropical to cold due to large altitude differences. Mostly, the people are living with passive means of cooling without mechanical cooling, have already discussed in our last article which has been published on 22th February 2022 in Gorkha Express Weekly. The indoor thermal environment depends on climatic condition. Extremely hot and cold condition could result in not only difficulty in sleeping but also affect health, discomfort, illness and even death.
In Nepal, the wooden houses (Moulik Raithane Ghar) are made by locally available materials which is well adapted in sub-tropical climatic region can be seen following photograph. But concrete houses are made by market materials which are not necessarily product locally. These materials are not only expensive but also environmentally and ecologically inappropriate than locally available materials. In the Terai area of Nepal, most of the houses (74.8%) are designed not only based on local needs, the availability of construction materials and reflecting local traditions but also thermal environment. Thermal environment is one of the most important factors that can affect human sleep. Very high indoor air temperature decreases slow wave sleep and increased the frequency and duration of wakefulness studied by Mizuno and Mizuno 2012. Therefore, thermally comfortable sleeping environment is important for human health. Which is only possible in traditional houses (Moulik Raithane Ghar) not so concrete houses in Terai region of Nepal. These types of research are necessary because sleep is important for health and comfort. That’s why, I try to evaluate base on my field study about the sleeping time temperatures differences between wooden (Moulik Raithane Ghar) and concrete houses in sub-tropical climatic region in Nepal.
Following Figure shows the results of one-day variation of indoor air temperature (Ti) and outdoor air temperature (To) in the wooden house (Moulik Raithane Ghar) and concrete house. Outdoor air temperature has affected the indoor air temperature. The night time and early in the morning time, the indoor and outdoor air temperatures tend to be lower than the day time. The variation of indoor air temperature in a wooden house is lower than that in a concrete house. The diurnal range of wooden and concrete house is 7°C and 9°C respectively. The average indoor air temperature in a wooden house is 3.2°C lower than a concrete house. It means that the wooden house is cooler than concrete house in summer. This may be due to the small size of the windows, thick wall to prevent outdoor heat.
As can be seen in Figure, the indoor air temperature for wooden house (Moulik Raithane Ghar) and concrete house and outdoor air temperature with sleeping time. The indoor air temperature is 25.3 to 33.1ºC in concrete house and 23 to 28ºC in wooden house. Thus, residents may find difficult to sleep in concrete houses. Considering the indoor air temperature of 32ºC, it affects to the sleeping quality, and the sleep quality is lower below indoor air temperature 23ºC and above 30ºC. This Result concluded that the wooden house (Moulik Raithane Ghar) is better than the concrete house in sub-tropical regions of Nepal. This article may encourage and direct the Nepalese government to make rational policy and plans for future.