Manipulation of Thermal Mass with Natural Ventilation; Application for Residential Buildings in Tropics

Abstract

This paper investigates the integration of thermal mass with natural ventilation for passive climate modification in residential buildings in tropics. Compact house forms found in historic world heritage site, Galle Fort, Sri Lanka is selected as the case study. In warm humid climates, the ambient daytime dry bulb temperature records around 34 degrees C or higher. This is quite extensive given the daytime humidity around 80 percent and the air velocity up to one meter per second. Since the indoor climate closely follows the outdoor climate, there is a need for lowering the swing of indoor air temperature below the level of ambient. Bioclimatic buildings (Olgyay, 1963) provide solution to these problems through climate responsive design. This can be effective in skin dependant buildings because of the potential interaction between Climate, Buildings and Occupants, but empirical evidence of the effectiveness of this approach is less visible (Ismail LH, 2006). The paper suggests opportunities for cooling indoors arising from the innovative use of thermal mass effect together with ventilation behavior in climate responsive building forms in warm humid climates. The research useshistoric colonial residential building as a point of departure since these buildings form a model which has been optimized through the experience of time. The building was tested by a field investigation using on- site thermal monitoring. Further the simulation based methodology is used for data evaluation thus highlighting the efficiency of night ventilation in the critical hot nights by transferring the heat from inside to outside with the air fluid effect of building section and envelope (grab the cool air from lower openings and remove the heated air from the upper openings) in maintaining in-door comfort throughout the day. The work evidenced supporting the passive influence of building section with night ventilation and manually ormechanically driven hybrid day ventilationwhich can be effective in improving thermal comfort without increasing the electricity demand. The significance of this lies in the need for cutting the energy demand for cooling and to avoid indoor overheating in tropics.