Effect of roof solar reflectance on the building heat gain in a hot climate

H Suehrcke; Eric L Peterson; N Selby

doi:10.1016/j.enbuild.2008.06.015

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Effect of roof solar reflectance on the building heat gain in a hot climate

Journal article

Peer reviewed

Effect of roof solar reflectance on the building heat gain in a hot climate

H Suehrcke, Eric L Peterson and N Selby

Energy and Buildings, Vol.40(12), pp.2224-2235

2008

DOI: https://doi.org/10.1016/j.enbuild.2008.06.015

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Abstract

Urban and Regional Planning

Environmental Engineering

roof solar absorptance

solar reflectance

roof heat gain

thermal resistance

hot climate

cool roof

The effect of the roof solar reflectance on the thermal performance of a building is often ignored. However, there are significant differences in heat gain from light and dark-coloured roof surfaces. In this paper an equation for the average daily downward heat flow of a sunlit roof is derived. Using building simulation, it is first shown that the thermal mass of the roof does not significantly affect the overall daily heat gain (although it causes a time lag and reduction in peak heat flow). As a consequence the daily heat gain from the roof may be estimated by integrating the equation for the steady-state downward heat transfer over the day. For north Australia the derived equation suggests that a light-coloured roof has about 30% lower total (air temperature difference and solar-driven) heat gain than a dark-coloured one. The effect of aging (change in solar reflectance with time) is considered in the calculations and a relationship between the solar absorptance of new and aged material is suggested. A classification of roof colours with respect to their solar absorptance (dark, medium, light and reflective) is proposed to enable a quick and simple assessment of the effect of roof colour on the heat gain and R-value.

Details

Title: Effect of roof solar reflectance on the building heat gain in a hot climate
Authors: H Suehrcke (Author) - James Cook University
Eric L Peterson (Author) - Victoria University
N Selby (Author)
Publication details: Energy and Buildings, Vol.40(12), pp.2224-2235
Publisher: Elsevier S.A.
Date published: 2008
DOI: 10.1016/j.enbuild.2008.06.015
ISSN: 0378-7788
Organisation Unit: University of the Sunshine Coast, Queensland
Language: English
Record Identifier: 99449748902621
Output Type: Journal article

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Collaboration types: Domestic collaboration
Web Of Science research areas: Construction & Building Technology; Energy & Fuels; Engineering, Civil

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