Analysis of microclimatic diversity and outdoor thermal comfort perceptions in the tropical megacity Dhaka, Bangladesh

• Published in: Building and environment 2015-12, Vol.94, p.734-750
• Main Authors: Sharmin, Tania, Steemers, Koen, Matzarakis, Andreas
• Format: Article
• Language: English
• Subjects: Outdoor thermal comfort; Tropical hot-humid climate; Urban geometry; Urban microclimate
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2015.10.007

The study has observed microclimatic conditions in residential, commercial and educational areas in Dhaka city. Comfort surveys were carried out along with microclimatic measurements. Findings suggest, urban forms that are more variable with irregular plot sizes and building heights, mostly in traditional areas, have positive responses with respect to the synoptic climate, while planned areas with uniform plot sizes and height, shows a tendency to develop daytime urban heat island effect. An east–west orientated street in a formal residential area was found to be 1 °C–3.8 °C warmer than a street in a traditional residential area in the same orientation. It is apparent that the differences are directly linked to the specific geometric pattern of the areas and can be defined by the parameters like uniformity versus diversity and compactness versus openness. Uniform heights, equal building separation and plot sizes can lead to harsher urban microclimate, while variety in these may foster positive changes. Lack of such variety can even affect compact urban areas. This is also evident from the analysis of pedestrian's responses in the case-study areas. Pedestrians in the formal planned areas or less diverse traditional areas were found to be less comfortable than those in the more variable areas. A statistical analysis of climatic variables and thermal sensation showed moderately strong and significant correlations. These reveal that urban geometry and the resultant climatic variables may not be the only, but one of the most important factors for governing the outdoor thermal comfort sensation in a tropical climate. •We study the effect of urban form on urban microclimate and outdoor thermal comfort.•Variable urban form has positive effect towards urban microclimate in warm climates.•Uniform urban forms can increase urban heat island impact in warm-humid climate.•Traditional areas have lower air and mean radiant temperature than planned areas.•People in diverse and variable traditional areas are reported more comfortable.