White Roofs on Townsville Buildings Scientific analysis shows that a white roof can substantially reduce air conditioning loads and make buildings more comfortable. |
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Until several years ago engineers were rarely able to calculate the response of a building that is subject to time varying interior and exterior thermal loads. This is because a large number of simultaneous equations were required. However, with the advent of inexpensive computing power and specialist software, thermal modeling of buildings is now possible. For example, Engineering Equation Solver (EES) is able to solve large sets of non-linear algebraic and differential equations. In this web page is presents an overview of the the use of EES to investigate the effect of roof colour / surface finish on human comfort and air conditioning load on a model building representative of a North Queensland home. The computer model building used for this assessment has no windows and its thermal response is driven solely by solar radiation on the roof surface. The model building features:
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White
roof and green roof side by side. Townsville buildings are rarely energy efficient. |
Despite common belief that galvanized metal surfaces reflect solar radiation, corroded (weathered) galvanized surfaces absorb up to 80% of sunlight. Moreover, radiative heat loss to the sky is very low. Combining high solar absorbance with low thermal heat loss produces roof surface temperatures can reach nearly 60 degrees Celsius. On the other hand, the temperatures of a white roof under similar conditions stay below 35 degrees Celsius. Findings:
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This web site is an overview of: Contact: Disclaimer: This information is made public upon request by Townsville City Council. The paper has not been fully peer reviewed. Users of the information in this overview report do so at their own risk. |