Assessment of Thermal Comfort in Respect to Building Height in a High-Density City in the Tropics

Mishima Nobuo,Shoichi Kojima,Anisha Noori Kakon,Taguchi Yoko

doi:10.3844/ajeassp.2010.545.551

Abstract

Problem statement: The significance of urban design and planning in t he tropics lies mostly on its climatic and regional concerns. Among many design parameters, building height is an important parameter which affects thermal climate i n the city considerably. This study investigated th e effect of building height on outdoor thermal comfor t 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 residenti al 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 to ol 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 t he existing canyon. In case of proposed canyon, it was found that increased building height provides compa ratively 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 identif y 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 st ress in summer.

Highlights

Rapid urbanization in the tropics has brought in its wake many hitherto changes to the physical environment of the cities
Though some differences exist between temperature, relative humidity, air velocity and measurements and simulation, it is found that ENVI
The present study has compared the condition of thermal climate in an existing urban canyon and in the same canyon with increased building height

Summary

Introduction

Rapid urbanization in the tropics has brought in its wake many hitherto changes to the physical environment of the cities. Climate change is one of those that have large effects on the health and wellbeing of humans, animals and plants in a city. The integration of climate dimension in the city planning and design process has become a vital issue now-adays. Urban design and planning policy instruments for the mitigation of the negative impacts of tropical urban climate remains largely unexplored in this region (Emmanuel, 2005). Among the urban design elements, urban density is an important one. A given urban density can result from independent design features, which affect urban climate in different ways such as: Fraction of urban land covered by buildings, distances between buildings, including streets’ width, average height of buildings (Watson, 2003)

Methods

Results

Conclusion