An investigation of thermal comfort conditions under rock formations m Sri Lanka

Behaviour of a rock as a barrier of heat differs so much from the behaviour of a conventional insulator. In thecase of an insulator the factor that governs the heat exchange is Thermal Conductivity. But rocks, being massive in both density and scale, the Heat Capacity of the material largely effect the heat flow. And under natural thermal environment, the heat flow will never reach a steady state. The governing factor of heat flow here is Thermal Diffusivity. This ever-transient heat flow problem is so complex that it is hardly studied. This report is the fore runner to a research or the capability to utilize natural rock for motions in architecture to create advanced thermal environment. The main objective is to verify whether rocks do effect the thermal environment of their surrounding to a level worthwhile to be studied. 1.INTRODUCTION In tropical countries like Sri Lanka it can be seen that people find the interior of buildings too warm and humid. It is unusual for those whose evolution has been taken place in the same climate through thousands of years, to feel uncomfortable in the same climate. Only a little change of the basic parameters of climate such as mean temperature, humidity and annual rainfall has taken place within the time duration of human evolution. Therefore it is likely that this discomfort is due to the nature of living spaces and the thermal properties of the materials used in modern buildings . The absence of trees also may have an effect on reducing thermal comfort today. Rocks are elements closely related to human life from the beginning of human civilization. Their effect on formation of human cognition in formation of the concept of home (rock caves), beliefs, religion and feelings of awe and respect is enormous. Looking at a rock one can perceive things beyond its physical existence rocks have instinctive meanings. There is the possibility to use rocks as strong architectural elements that evoke instinctive references once laid deep in human mind. Natural rock caves were the earliest living spaces used by human beings. Spaces among rocks have been converted to living spaces in Sri Lankan meditation centers and temples of early days. These conversions seem to work well from the point of view of thermal comfort. These facts lead us to think about the possibility of integration of rocks to contemporary S.i Lankan architecture in order to create better living spaces with better thermal comfort levels achieved with passive means. Many rocky sites can be found in Sri Lanka that are ignored and considered as barren lands. There are stone pits that end up as useless ponds of dirty water. The possibility of converting these places to habitable spaces is yet to be found out. Therefore it was decided to check whether the so-called living spaces among rocks really have better comfort levels. Level of thermal comfort of some selected rock caves and spaces created among rocks are measured and compared with that of immediate surrounding. This is to examine whether or not rocks have potential to provide improved thermal comfort levels. The facts how and to what extent rocks have affected comfort levels or what is the exact or mean comfort level of individual space is beyond the scope of this study. Measurements are carried out with a dry bulb and wet bulb thermometer. Measurements of the selected spaces and the immediate surroundings were taken simultaneously. These data are used to find out the level of thermal comfort of the places. We decided to use the Temperature-Humidity Index developed by Thorn (1959) because in this method the level of comfort is indicated in a numerical value so that the comfort levels can be numerically compared. 2.Back Ground Temperature-Humidity Index (THI) is defined thus THI= 0.72X(TD+TW)+40.6 Where TD and TW are dry bulb and wet bulb temperatures respectively. THI<60 1 0 0 % of the subjects felt uncomfortably cold. 60

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