Energies 2013, 6(2), 598-618; doi:10.3390/en6020598

Green-Roof Effects on Neighborhood Microclimate and Human Thermal Sensation

Department of Geography, The University of Hong Kong, Pokfulam Road, Hong Kong, China
* Author to whom correspondence should be addressed.
Received: 30 November 2012; in revised form: 21 January 2013 / Accepted: 21 January 2013 / Published: 25 January 2013
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Abstract: Green roofs have been recognized as an effective sustainable design tool to mitigate urban heat island (UHI) effects. Previous studies have identified green-roof benefits in cooling and energy-conservation at the building scale, with limited exploration of the wider influence on neighborhood microclimate and human thermal comfort (HTC). This paper investigated the impacts of community-scale green-roof installation on air temperature and HTC in five typical residential neighborhoods of subtropical Hong Kong. The microclimate models ENVI-met and RayMan permitted studies of two main green-roof scenarios, namely extensive (EGR) and intensive (IGR). Microclimatic monitoring data from a local experimental green-roof site validated the modeling methods. The results verified that green-roof cooling effects were not restricted to rooftops, but extended to the ground to improve neighborhood microclimate. EGR reduced pedestrian-level air temperature by 0.4–0.7 °C, and IGR by 0.5–1.7 °C, with maximum effect in open-set low rise sites. Coverage by building footprints and building height dampened lateral and vertical advection of cool air generated by green roofs. Roof greening also improved notably the rooftop-podium level HTC. Diurnal duration of high heat stress was reduced by 6–9 h for EGR scenarios, and 9–11 h for IGR. The findings indicated that large-scale green-roof installation could bring neighborhood-wide cooling, mitigate urban heat island effect, and furnish more comfortable thermal environment for urban residents.
Keywords: green roof; climate change; cooling effect; human thermal comfort; urban heat island; compact city; sustainable urban design

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MDPI and ACS Style

Peng, L.L.; Jim, C.Y. Green-Roof Effects on Neighborhood Microclimate and Human Thermal Sensation. Energies 2013, 6, 598-618.

AMA Style

Peng LL, Jim CY. Green-Roof Effects on Neighborhood Microclimate and Human Thermal Sensation. Energies. 2013; 6(2):598-618.

Chicago/Turabian Style

Peng, Lilliana L.; Jim, C. Y. 2013. "Green-Roof Effects on Neighborhood Microclimate and Human Thermal Sensation." Energies 6, no. 2: 598-618.

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