Thermal environment in residential areas of metropolitan Dhaka: effects of densification

Abstract

Rapid urbanization and high population growth rate have made Mega-City Dhaka a container of several millions of citizen. To accommodate influx of huge population within the limited buildable land ResidentIal Districts (RD) are gradually allowing more and more density, in terms of physical building mass, energy usage, transportation, etc. Thermal Environment (TE) of these areas is obviously affected by this densification process. To investigate into the climatic effects of such densification four different types of RD (Sutrapur, Dhanmondi RIA, BUET Teachers' Quarter and Banani RIA) are selected within Dhaka Metropolitan Area (DMA) covering both formal and informal sectors. Existing physical characteristics, which determine the overall settlement pattern, of all four RD are analyzed in terms of Floor Area Ratio (FAR), Ground Coverage (OC), Hard to Soft Surface Ratio (HSSR), Population Density, Sky-Line and Setback Space. Out door environment is largely dependent on natural climatic pattern, which is almost impossible to control. On the other hand, indoor environment is largely dependent on its internal space layout, enclosure characteristics, use pattern, etc., which are controlled by individual choices. Between indoor and outdoor spaces there is a Transitional Space (TS) ([ext 4.2.2) through which a man-made spaee actually breathes into the natural environment. Thermal environment of TS is modified by the overall settlement pattern. That is why temperature, relative-humidity and wind_gradient data are collected from four TS at four RD. These data are compared among each other and also compared with the data that are collected from Dhaka meteorological station at Agargaon. During April, May and June (summer) people of Dhaka experiences the most hot..<\iscomfort and get heavily dependent on active means of climatic control putting tremendous pressure on scarce energy supply. Therefore the month May is selected for survey and climatic data collection. Finally, the physical characteristics are correlated with the climatic data ofTS of all four RDs and the positive and negative effects of densification pattern on IE are pointed out. The study ended up with some specific recommendations that can be considered in modifYing Building Construction Rules (BeR) to facilitate passive climatic control and thereby to create more sustainable residential environment in DMA.