Abstract
Colombo, with its rapid development, is experiencing an influx of high-rise developments. These developments create a significant influence on the microclimate of the area around them, and therefore impact outdoor thermal comfort. With the intension of mitigating outdoor thermal comfort concerns, the enhancement of the vegetation cover is an often-proposed strategy. This is a research initiative to ascertain the optimum vegetation cover percentage to achieve outdoor thermal comfort around high-rise developments, utilising Havelock City, Colombo, Sri Lanka as a case study. A computer simulation process is adopted, using the software ENVI-met, to explore the optimum form and coverage of vegetation for outdoor thermal comfort. Results show, overall thermal comfort levels diminish, with the increased infusion of vegetation. Vegetation cover had a little or no impact in the daytime, while the strategy had distinct negative impacts in the night-time. The nature of the built morphology of the development together with the vegetation cover increase is shown to have significant impact on wind movement and nocturnal heat loss, therefore outdoor thermal comfort levels. Conclusions highlight the need for the extensive exploration of morphological studies, while encompassing key amelioration strategies, particularly for the high-rise development typology.
Highlights
High-rise developments play an important role in modern cities and its urban form
This study considered the hottest day of the year; it is seen that predicted mean vote (PMV) values have exceeded defined limits
KEY FINDINGS AND IMPLICATIONS FOR DESIGN 5.1.1 Vegetation Cover changes utilised in the high-rise development of Havelock City, have little no impact in the daytime hours of the day
Summary
High-rise developments play an important role in modern cities and its urban form. Growth of the population and its ever-increasing concentration to cities has become a necessity in the pursuit of economic upliftment and a better quality of living. High-rise buildings and developments significantly influence the urban climate of cites at all scales, including the microclimate of the immediate context. While high-rise developments can have a significant positive impact on social and economic elements of a city, “the high-rise building typology is not usually considered environmentally sustainable, due to its intensive use of energy, material and other resources during its whole life cycle, it has merits such as saving land resources and transportation costs” (Goncalves, 2010). High-rise developments alter its surrounding thermal environment in terms of; Urban geometry – variations in building heights and distances in-between them; Local climate – relative humidity, external air temperatures and prevailing wind speeds and directions; Orientation and overshadowing – position of tall buildings with respect to south (northern hemisphere) and its exposure to solar radiation and overshadowing over low rise buildings within the cluster; Solar access, solar radiation and albedo; and Urban canyons. In addition to reflecting direct solar radiation high-rise buildings absorb and reflect solar radiation from other buildings. (Arslan and Sev, 2014)
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