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Article: Weather effect on thermal and energy performance of an extensive tropical green roof

TitleWeather effect on thermal and energy performance of an extensive tropical green roof
Authors
KeywordsCooling Load
Energy Conservation
Extensive Green Roof
Heat Flux
Passive Cooling
Thermal Performance
Issue Date2012
PublisherUrban und Fischer Verlag. The Journal's web site is located at http://www.elsevier.com/locate/ufug
Citation
Urban Forestry And Urban Greening, 2012, v. 11 n. 1, p. 73-85 How to Cite?
AbstractThis study investigated the weather effect on thermal performance of a retrofitted extensive green roof on a railway station in humid-subtropical Hong Kong. Absolute and relative (reduction magnitude) ambient and surface temperatures recorded for two years were compared amongst antecedent bare roof, green roof, and control bare roof. The impacts of solar radiation, relative humidity, soil moisture and wind speed were explored. The holistic green-roof effect reduced daily maximum tile surface temperature by 5.2°C and air temperature at 10cm height by 0.7°C, with no significant effect at 160cm. Green-roof passive cooling was enhanced by high solar radiation and low relative humidity typical of sunny summer days. High soil moisture supplemented by irrigation lowered air and vegetation surface temperature, and dampened diurnal temperature fluctuations. High wind speed increased evapotranspiration cooling of green roof, but concurrently cooled bare roof. Heat flux through green roof was also weather-dependent, with less heat gain and more heat loss on sunny days, but notable decline in both attributes on cloudy days. On rainy days, green roof assumed the energy conservation role with slight increase instead of reduction in cooling load. Daily cooling load was 0.9kWhm -2 and 0.57kWhm -2, respectively for sunny and cloudy summer days, with negligible effect on rainy days. The 484m 2 green roof brought potential air-conditioning energy saving of 2.80×10 4kWh each summer, equivalent to electricity tariff saving of HK$2.56×10 4 and upstream avoidance of CO 2 emission of 27.02t at the power plant. The long-term environmental and energy benefits could justify the cost of green roof installation on public buildings. © 2011 Elsevier GmbH.
Persistent Identifierhttp://hdl.handle.net/10722/157932
ISSN
2015 Impact Factor: 2.006
2015 SCImago Journal Rankings: 1.193
ISI Accession Number ID
Funding AgencyGrant Number
railway company KCRC (recently merged with MTRC)
Funding Information:

We acknowledge with gratitude the research grant support kindly provided by the railway company KCRC (recently merged with MTRC). We are especially indebted to Mr. Yun Tai Li for his bold vision and determination to install a green roof on the Tai Po Railway Station and to fund our scientific study to ascertain its environmental benefits. The kind advice and help offered by Francis Goh, Brandon Chow, Grace Kwong, Jeannette Liu, Raymond Wai Hung Law and Wing Yiu Wong are gratefully appreciated.

References

 

DC FieldValueLanguage
dc.contributor.authorJim, CYen_US
dc.contributor.authorPeng, LLHen_US
dc.date.accessioned2012-08-08T08:56:23Z-
dc.date.available2012-08-08T08:56:23Z-
dc.date.issued2012en_US
dc.identifier.citationUrban Forestry And Urban Greening, 2012, v. 11 n. 1, p. 73-85en_US
dc.identifier.issn1618-8667en_US
dc.identifier.urihttp://hdl.handle.net/10722/157932-
dc.description.abstractThis study investigated the weather effect on thermal performance of a retrofitted extensive green roof on a railway station in humid-subtropical Hong Kong. Absolute and relative (reduction magnitude) ambient and surface temperatures recorded for two years were compared amongst antecedent bare roof, green roof, and control bare roof. The impacts of solar radiation, relative humidity, soil moisture and wind speed were explored. The holistic green-roof effect reduced daily maximum tile surface temperature by 5.2°C and air temperature at 10cm height by 0.7°C, with no significant effect at 160cm. Green-roof passive cooling was enhanced by high solar radiation and low relative humidity typical of sunny summer days. High soil moisture supplemented by irrigation lowered air and vegetation surface temperature, and dampened diurnal temperature fluctuations. High wind speed increased evapotranspiration cooling of green roof, but concurrently cooled bare roof. Heat flux through green roof was also weather-dependent, with less heat gain and more heat loss on sunny days, but notable decline in both attributes on cloudy days. On rainy days, green roof assumed the energy conservation role with slight increase instead of reduction in cooling load. Daily cooling load was 0.9kWhm -2 and 0.57kWhm -2, respectively for sunny and cloudy summer days, with negligible effect on rainy days. The 484m 2 green roof brought potential air-conditioning energy saving of 2.80×10 4kWh each summer, equivalent to electricity tariff saving of HK$2.56×10 4 and upstream avoidance of CO 2 emission of 27.02t at the power plant. The long-term environmental and energy benefits could justify the cost of green roof installation on public buildings. © 2011 Elsevier GmbH.en_US
dc.languageengen_US
dc.publisherUrban und Fischer Verlag. The Journal's web site is located at http://www.elsevier.com/locate/ufugen_US
dc.relation.ispartofUrban Forestry and Urban Greeningen_US
dc.subjectCooling Loaden_US
dc.subjectEnergy Conservationen_US
dc.subjectExtensive Green Roofen_US
dc.subjectHeat Fluxen_US
dc.subjectPassive Coolingen_US
dc.subjectThermal Performanceen_US
dc.titleWeather effect on thermal and energy performance of an extensive tropical green roofen_US
dc.typeArticleen_US
dc.identifier.emailJim, CY:hragjcy@hkucc.hku.hken_US
dc.identifier.authorityJim, CY=rp00549en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1016/j.ufug.2011.10.001en_US
dc.identifier.scopuseid_2-s2.0-84856373255en_US
dc.identifier.hkuros207789-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-84856373255&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume11en_US
dc.identifier.issue1en_US
dc.identifier.spage73en_US
dc.identifier.epage85en_US
dc.identifier.isiWOS:000301309600009-
dc.publisher.placeGermanyen_US
dc.identifier.scopusauthoridJim, CY=7006143750en_US
dc.identifier.scopusauthoridPeng, LLH=54385592500en_US

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