Green-roof effects on neighborhood microclimate and human thermal sensation

Lilliana L.H. PENG, Chi Yung JIM

Research output: Contribution to journalArticlespeer-review

172 Citations (Scopus)


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 oC, and IGR by 0.5-1.7 oC, 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. Copyright © 2013 by the authors.

Original languageEnglish
Pages (from-to)598-618
Issue number2
Publication statusPublished - 25 Jan 2013


Peng, L. L. H., & Jim, C. Y. (2013). Green-roof effects on neighborhood microclimate and human thermal sensation. Energies, 6(2), 598-618. doi: 10.3390/en6020598


  • Green roof
  • Climate change
  • Cooling effect
  • Human thermal comfort
  • Urban heat island
  • Compact city
  • Sustainable urban design


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