Effect of Roof Solar Reflectance on the Building Heat Gain in a Hot Climate

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Suehrcke, Harry, Peterson, Eric L and Selby, Neville (2008) Effect of Roof Solar Reflectance on the Building Heat Gain in a Hot Climate. Energy and Buildings, 40 (12). pp. 2224-2235. ISSN 0378-7788


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.

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Item type Article
URI https://vuir.vu.edu.au/id/eprint/3979
DOI 10.1016/j.enbuild.2008.06.015
Official URL http://www.sciencedirect.com/science/article/pii/S...
Subjects Historical > FOR Classification > 0907 Environmental Engineering
Historical > SEO Classification > 9609 Land and Water Management
Historical > Faculty/School/Research Centre/Department > Institute for Sustainability and Innovation (ISI)
Historical > Faculty/School/Research Centre/Department > School of Engineering and Science
Keywords ResPubID16080, roof solar absorptance, solar reflectance, roof heat gain, thermal resistance, hot climate, cool roof
Citations in Scopus 175 - View on Scopus
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