Problem statement: The significance of urban design and planning in the tropics lies mostly on its climatic and regional concerns. Among many design parameters, building height is an important parameter which affects thermal climate in the city considerably. This study investigated the effect of building height on outdoor thermal comfort during the daytime in summer in Dhaka, Bangladesh which is a high density city located in tropical climate zone. This study emphasized on pedestrian comfort condition in a planned residential area in the city. Approach: Thermal comfort was assessed in terms of Temperature-Humidity-Index (THI) which uses air Temperature (T a ) and Relative Humidity (RH). Measurements were carried out in a typical summer day. In addition, to simulate the urban thermal climate, a 3D numerical simulation tool ENVI-met was used. Results: Simulated results showed close agreement with the measured data in case of existing canyon and thus the validity of the present numerical simulation was confirmed. Results showed that in case of existing canyon with average building height of 4-5 storied, THI lies in the discomfort level. A canyon was proposed by increasing the building height to 8-10 storied in the existing canyon. In case of proposed canyon, it was found that increased building height provides comparatively comfortable condition than the existing case during day time. Moreover, mean radiant temperature (T mrt ), surface Temperature (T s ) and wind speed were included in the present study to identify the effects of building height on these factors. Conclusion: The present study had an implication on the urban design process to achieve a more comfortable urban environment by mitigating heat stress in summer.

The thermal comfort in urban canyons of a high density city is a very challenging issue for urban planners and designers, especially in hot humid tropical zone. The present study aims to evaluate the effects of a newly promulgated building construction rules in respect of thermal climate for Dhaka, Bangladesh, a region characterized by high density area with tropical climate. Three different urban canyons from three areas were considered which almost represents the whole city. Measurements were carried out to assess the existing thermal climate in the city canyons. Further, three model canyons were configured according to the new rules of ground coverage, floor area ratio (FAR) and site setback. A three-dimensional numerical model with high spatial and temporal resolution was used to investigate the microclimatic changes within the urban environments. Model calculations were run for a typical summer day. The thermal climate was evaluated based on air temperature Ta, surface temperature Ts, relative humidity RH, and wind speed in the existing and model canyons. For thermal comfort assessment the temperature humidity index (THI) was considered in this study. The results showed that the outdoor spaces of the study areas are thermally uncomfortable and the new building construction rules hardly improve the conditions in general. However, THI decreases in a canyon where sky view factor (SVF) decreases in the model canyon than the existing one. In addition, the surface temperature Ts and air temperature Ta do not show the same picture. Furthermore, the wind speed increases in all the model canyons as the site setback allows wind flow uniformly inside the canyons. Keywordssimulation, urban canyon, sky view factor (SVF), thermal climate, air temperature, relative humidity, temperature humidity index (THI)

Now-a-days the industrial revolution is taking place in Bangladesh like the other developing countries. The number of industries is increasing resulting the increased number of migrant people as workers. This large amount of people demands housing. To meet this demand, the land owners are constructing houses without considering the quality. This study tends to explore the existing housing condition of garment workers in a sub-city Savar, near Dhaka. All the information about the garments workers were collected by observation, questionnaire survey and personal interview method. The aspects that mainly considered in this study were type and material of house, size of room and occupancy, related facilities and services such as water supply, electricity, drainage, solid waste management and so on. It was found that the garment workers usually rent a single room in a group housing whatever the family size is. In a group housing a minimum of 5 and maximum 35 family lived. They shared the kitchen, toilet and bathroom. A considerable number of workers (about 40%) were still use wood in the kitchen. Corrugated Iron sheet was the main housing material as well as brick, concrete, bamboo and mud were used. The workers living in the study area faced the problems of frequent load shedding, lack of proper drainage system and absence of solid waste management system. In fact, the garment workers are rural migrants and inexperienced in urban life. They are not concerned about the facilities they should get with housing.

In this paper, the influence of building height on the thermal climate in urban canyons is discussed. The investigation was carried out using a three-dimensional numerical model with high spatial and temporal resolution that simulated the microclimatic changes in urban environments. Model calculations were performed for a typical summer day in Dhaka, Bangladesh, a city in South Asia with a high population density and tropical climate. Two existing urban canyons in the city center with different height to width ratios, and projected canyons with increased building heights were investigated for daytime conditions. The thermal climate was evaluated on the basis of solar radiation, air temperature T a , and mean radiant temperature T mrt , mostly along the pedestrian ways. The results show that with respect to daytime thermal climate depending on T a , greater building height was more advantageous in the case of shallow canyons than for deeper canyons. However, the mean radiant temperature T mrt on the pedestrian ways was found to be 30 -40°C higher than T a for sunny conditions; however, for shaded conditions, the difference was minimal. Finally, considerable decreases in T mrt were found in projected canyons compared with existing canyons, especially during those times of the day when there is shade.