Dr. Basudev Gautam - - - -
Nepal is a landlocked country located between India to the east, south, and west and China to the north. It has small land area of 1,47,181 km2 with diverse climatic and geographical variations. It is broadly classified into three ecological regions: mountain, hilly and terai regions, all of which extend from east to west. Climatic features of the three regions can be seen in a short distance from south to north. Northern mountain, middle hilly and southern terai regions are dominated respectively by cold, temperate and sub-tropical climate. Each region has its distinctive housing patterns, cultural differences including so-called adaptive behaviors to avoid thermal discomfort from the local outdoor environmental conditions. The traditional skills of construction, one of whose major objectives must have been to mitigate indoor thermal conditions, have been handed over from one generation to another since old days with almost no modification, but they are being replaced by the contemporary ways of construction like modern design and technology including artificial materials (https://doi.org/10.1016/j.jobe.2019.100886).
Every year new houses are being built in Nepal as a part of urbanization and modernization. Under this circumstance, it is important to know the state of thermal comfort experienced by Nepalese people with the living condition in traditional houses, which has made the local people develop their respective unique culture. Although the surrounding countries, India and Pakistan, have their own thermal-comfort standards, the Nepalese government has not yet established any thermal-comfort standard. It is necessary also Nepalese government to establish the thermal-comfort standard and make rational policy and plans in the future.
Each year, Nepalese peoples living in not only sub-tropical region in summer have to face extreme heat but also cold region in winter have to face extreme cold causing various problems ranging from discomfort to illness and death. Indoor environment is extremely hot, it directly affects human health, and mortality rate rises evidently with increasing hot stress. Some researchers resulted that the 45–64 years age-group is a risk group to be taken into account when it comes to considering the health-related effects of temperature extremes. The elderly and infants are more at risk from exposure to low temperature presented. Exposure to high temperatures can increase the risk of heat stroke, and health problems such as respiratory and cardiovascular hospitalizations and deaths. In Nepal, under a high emissions scenario heat-related death in the elderly (65+ years) are approximately 4 deaths per 100,000 annually between 1961 and 1990 reported by World Health Organization (2015). To avoid discomfort caused by hotness in sub-tropical region, people take a variety of actions such as staying on the top of roof, in semi-open spaces or front yards during the evening time, drinking a lot of cold drinks, taking showers often to get rid of sweat, using fans and wearing less clothing for the ease of releasing heat from their bodies. And other hand to avoid discomfort caused by coldness in cold region, people take a variety of actions such as staying near firewood, drinking a lot of hot tea or butter tea, closing the all openings and wearing heavy clothing for the easy of releasing cold from their body.
Nepal has climatic variation from cold to sub-tropical regions. Climate affect the building type, thermal environment and human behaviors. These two things such qualitative observation can be done everybody. But our focus is to investigate these two things; (1) climate affect the buildings types, thermal environment and (2) climate affect the human behaviors in quantitative way (https://doi.org/10.1016/j.buildenv.2020.107237). We tried to know how the thermal environment indoors in originally people houses in respective regions. Now a days, in Nepal many people tend to move from temperate and cold climate to sub-tropical climate because of a variety of issues in the society and easy to live and so on. Hugged identified two types of people local and migrant. Climate affect people behaviors, buildings types if they move their perception could be different or not? So, we tried to answer whether there is a difference or not? We found that there are some differences; behaviors and also the limit of temperature value of performance and so on.
The thermal environment that is the defined air temperature, surface temperature, air velocity and so on should be identical. But they’re missing is the culture; including the food we eat, the clothing we wear and what kind of houses we are living in. People have natural tendency to adapt to changing conditions in their environment. If a change occurs to produced discomfort, people respond in ways which tend to restore their thermal comfort (changing clothing insulation, changing posture, opening or closing the openings, switching on or off the fans, increasing or decreasing the activities level). This kind of natural tendency of making people themselves comfortable is expressed in the adaptive thermal comfort. Whenever, we visited some places in different parts of Nepal, the way of living quite different than developed countries. The buildings constructions find different, especially the local houses were different. The local climate is different availability of the building’s materials and structure also different. Energy balance, physically speaking human beings is the same that is one thing quite important. There are localities these two things not well balance this is the reason why the adaptive thermal comfort approach comes up making field surveys, collecting votes.
Two kind of thermal factors that affect temperature of the room and human comfort are called physical and personal factors. The physical factors include; air temperature, mean radiation temperature, relative humidity and air velocity. The indoor air temperature of a building will change depending on the temperature outside. The walls and insulations are playing important role to change the indoor temperature. It can be said that if indoor temperature is extremely low or high, it directly affects to human health. The mortality rate with increasing cold stress. The elderly and infants are more vulnerable from exposure to low temperature. The body’s reaction to low temperature includes thickening of the blood and hypertension. The indoor environment is also affected by the residents inside the building and the activity they are doing. The mean radiant temperature also affects the human comfort. The mean radiant temperature is defined as the temperature of a uniform enclosure with which a small black sphere at the test point would have the same radiation exchange as it does with the real environment. The radiation is averaged for all directions and so the resulting ‘mean radiant temperature’ has a single value for any particular point in the room, the distribution of radiation from different directions then the mean radiant temperature will be sufficient. The relative humidity is another important factor that affects the human comfort. It is a considerable variable to measure only in warm and hot condition. The relative humidity is the percentage of water vapor saturation that is in the air. Although, most of the researchers suggested their research result about relative humidity; it is necessary that the water vapor pressure as an index of humidity, rather than relative humidity. The air movement is another important factor for human comfort; this is the movement of the air throughout a building or a room. In natural ventilated buildings, especially in a hot climatic region, air movement will have played most important role on the thermal comfort of the residents.
Another personal factors that can also affect the human comfort. Mainly, there are two personal factors; one is the clothing insulation and other one is the metabolic rate that affect the human comfort. Thermal comfort is very much dependent on the insulating effect of clothing on the wearer. Wearing too much clothing may be heat stress even if the environment is not considered warm or hot. If clothing does not provide enough insulation, the wearer may be at risk from cold injuries such as frostbite or hypothermia in cold conditions. Clothing is both a potential cause of thermal discomfort as well as a control for it as we adapt to the climate in which we work. It is important to identify how the clothing contributes to thermal comfort or discomfort. Metabolic rate; when more physical work we do, the more heat we produce. If more heat we produce, the more heat needs to be lost so we don’t overheat. The impact of metabolic rate on thermal comfort is critical. A person’s physical characteristics should always be tolerated in mind when considering their thermal comfort, as factors such as their size and weight, age, fitness level and sex can all have an impact on how they feel, even if other factors such as air temperature, humidity and air velocity are all constant.
The following Figure shows a schematic relationship between the types of built-environment technology and those of associated human behavior. The horizontal axis represents technology and the vertical axis represents behavior. The leftist extreme of the horizontal axis indicates such as case as local traditional passive technology alone, while the rightist extreme indicates such a case equipped fully with active technology alone. The former must necessitate very active behavior of the people for restoring their thermal comfort indoors, while on the other hand, the latter requires the least passive behavior, because theoretically speaking the active technology can do everything. In this diagram, the present condition of the traditional houses and their lifestyle are positioned in the area “T”, since it is hard to sustain the indoor environmental condition sufficiently with old and poor building envelope system alone, people need to take a lot of behaviors for avoiding thermal discomfort. Contemporary houses having mechanical systems for heating and cooling especially in the cities on developed countries are positioned in the area “U”; people may be less active, that is, passive in behavior. In either area “T” or “U”, they lack in optimal health, since the active systems may provide too little opportunities of the occupants’ behavior, while the passive system alone may necessitate too much of occupants’ behavior. In order to clarify the conventional path and propose path for developing country as the future target for either of “T” or “U”, it must be helpful to understand how the people try to restore their thermal comfort in traditional houses by changing clothes and doing other activities. It should be good to extract the positive aspects of traditional lifestyle and inherit them as the portion of futuristic lifestyle.
Figure. Schematic diagram of built-environmental technology and human behaviors
To preserve traditional constructing technology (Moulik Raithane Ghar), we have to make such a policy that the traditional technology is to be improved with some modern skills without deteriorating the cultural norm by keeping an eye on positive aspects of traditional houses (Moulik Raithane Ghar) that should be preserved and inherited into the future. One of the aspects to be improved while keeping the tradition skill must be better thermal comfort. For this purpose, we need to know how the people living in different climatic regions of Nepal achieve their thermal comfort in their respective traditional houses by taking various adaptive behaviors such as using the fan, shitting under the shade, using light clothes, and swimming in summer and use of the firewood, drinking hot tea, sitting on the sun light, and using heavy clothing for winter to mitigate the thermal comfort.
Good indoor environment is important for the success of a building, not only because it will make the people comfortable, but also because it will decide the energy consumption of the building and in the long run influence of economy and sustainability. “Thermal comfort as the condition of mind which expresses satisfaction with the thermal environment”, defined by ASHRAE stander 55 (2013). Thermal comfort standards are required by building designer and engineers to provide the indoor environment that the building people will find thermally comfortable which gives to people satisfactions. It was increasingly being felt by researchers such as Nicol, Humphreys, de Dear, Brager, Rijal and Gautam that the thermal comfort of the people was greatly influenced by perception, expectations, and opportunities to change clothing level and change immediate indoor environment etc. Tokyo Japan---- Email: - email@example.com