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Article: Effect of vegetation biomass structure on thermal performance of tropical green roof

TitleEffect of vegetation biomass structure on thermal performance of tropical green roof
Authors
KeywordsCanopy temperature inversion
Passive cooling
Perched thermal discontinuity
Subsurface thermal discontinuity
Suspended temperature inversion
Issue Date2012
PublisherSpringer Japan. The Journal's web site is located at http://www.springeronline.com/sgw/cda/frontpage/0,11855,5-10027-70-40628339-0,00.html
Citation
Landscape and Ecological Engineering, 2012, v. 8 n. 2, p. 173-187 How to Cite?
AbstractThe passive cooling effect of green roofs in humid, tropical Hong Kong was investigated with reference to three vegetated plots, grass, groundcover herb, and shrub, with contrasting growth form and biomass structure and a bare control plot. Temperature was monitored at 15-min intervals for a year at seven levels: high (H) at 200 cm, middle (M) at 60 cm, low (L) at 20 cm, surface, soil, rockwool (water storage), and roof-tile surface. The findings indicated the crucial roles played by biomass quantity and structural complexity in passive cooling functions. Temperature variations of vegetated roofs occurred mainly during the day, with lower maximum and minimum than the control, but they did not cool air at night better than the control. Control and grass surfaces were warmed above the ambient temperature, but groundcover and shrub surfaces followed the ambient. Despite complex biomass structure, shrub created the most extreme diurnal air temperature regime. Despite simple biomass structure, grass cooled air more effectively than groundcover and shrub. Four anomalies in the vertical temperature profile were detected. First, the grass roof cooled daytime near-ground air to create a suspended temperature inversion. Second, the stagnant air within the shrub biomass trapped heat to generate a daytime canopy temperature inversion. Third, the elevated branch-foliage biomass of groundcover and shrub brought passive cooling to form a perched thermal discontinuity. Fourth, the air gap of the plastic drainage layer arrested downward heat transmission in all vegetated plots to form a subsurface thermal discontinuity. The findings provide hints on species choice and design of green roofs. © 2011 The Author(s).
Persistent Identifierhttp://hdl.handle.net/10722/144913
ISSN
2015 Impact Factor: 0.597
2015 SCImago Journal Rankings: 0.247
ISI Accession Number ID
Funding AgencyGrant Number
Midland Charitable Foundation
Stanley Ho Alumni Challenge Fund
Funding Information:

I acknowledge with gratitude the grants kindly awarded by the Midland Charitable Foundation and the Stanley Ho Alumni Challenge Fund, and the green-roof donation by Cheung Shing Yuk Tong Limited. The field-work assistance provided by Jeannette Liu and W. Y. Wong is warmly appreciated.

 

DC FieldValueLanguage
dc.contributor.authorJim, CYen_HK
dc.date.accessioned2012-02-21T05:42:29Z-
dc.date.available2012-02-21T05:42:29Z-
dc.date.issued2012en_HK
dc.identifier.citationLandscape and Ecological Engineering, 2012, v. 8 n. 2, p. 173-187en_HK
dc.identifier.issn1860-1871en_HK
dc.identifier.urihttp://hdl.handle.net/10722/144913-
dc.description.abstractThe passive cooling effect of green roofs in humid, tropical Hong Kong was investigated with reference to three vegetated plots, grass, groundcover herb, and shrub, with contrasting growth form and biomass structure and a bare control plot. Temperature was monitored at 15-min intervals for a year at seven levels: high (H) at 200 cm, middle (M) at 60 cm, low (L) at 20 cm, surface, soil, rockwool (water storage), and roof-tile surface. The findings indicated the crucial roles played by biomass quantity and structural complexity in passive cooling functions. Temperature variations of vegetated roofs occurred mainly during the day, with lower maximum and minimum than the control, but they did not cool air at night better than the control. Control and grass surfaces were warmed above the ambient temperature, but groundcover and shrub surfaces followed the ambient. Despite complex biomass structure, shrub created the most extreme diurnal air temperature regime. Despite simple biomass structure, grass cooled air more effectively than groundcover and shrub. Four anomalies in the vertical temperature profile were detected. First, the grass roof cooled daytime near-ground air to create a suspended temperature inversion. Second, the stagnant air within the shrub biomass trapped heat to generate a daytime canopy temperature inversion. Third, the elevated branch-foliage biomass of groundcover and shrub brought passive cooling to form a perched thermal discontinuity. Fourth, the air gap of the plastic drainage layer arrested downward heat transmission in all vegetated plots to form a subsurface thermal discontinuity. The findings provide hints on species choice and design of green roofs. © 2011 The Author(s).en_HK
dc.languageengen_US
dc.publisherSpringer Japan. The Journal's web site is located at http://www.springeronline.com/sgw/cda/frontpage/0,11855,5-10027-70-40628339-0,00.htmlen_HK
dc.relation.ispartofLandscape and Ecological Engineeringen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong Licenseen_US
dc.subjectCanopy temperature inversionen_HK
dc.subjectPassive coolingen_HK
dc.subjectPerched thermal discontinuityen_HK
dc.subjectSubsurface thermal discontinuityen_HK
dc.subjectSuspended temperature inversionen_HK
dc.titleEffect of vegetation biomass structure on thermal performance of tropical green roofen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4551/resserv?sid=springerlink&genre=article&atitle=Effect of vegetation biomass structure on thermal performance of tropical green roof&title=Landscape and Ecological Engineering&issn=18601871&date=2011-05-06& spage=1&authors=C. Y. Jimen_US
dc.identifier.emailJim, CY: hragjcy@hkucc.hku.hken_HK
dc.identifier.authorityJim, CY=rp00549en_HK
dc.description.naturepublished_or_final_versionen_US
dc.identifier.doi10.1007/s11355-011-0161-4en_HK
dc.identifier.scopuseid_2-s2.0-84864123425en_HK
dc.identifier.hkuros207808-
dc.identifier.volume8-
dc.identifier.issue2-
dc.identifier.spage173en_HK
dc.identifier.epage187en_HK
dc.identifier.eissn1860-188Xen_US
dc.identifier.isiWOS:000306127000004-
dc.publisher.placeJapanen_HK
dc.description.otherSpringer Open Choice, 21 Feb 2012en_US
dc.identifier.scopusauthoridJim, CY=7006143750en_HK
dc.identifier.citeulike9275484-

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