Green roof in the desert: Comparing four alternative roof systems to a standard roof

The integration of vegetation, irrigation and natural materials like soil with the roof structure of a building may be a functional, ecologically sound, and cost-effective design strategy for reducing or dampening the effect of heat gain from solar radiation. This experiment explores the possibilities of reducing the energy consumption of buildings in the arid (hot and dry) climate of Phoenix, Arizona by analyzing the effect of solar radiation on different roof systems. Four roof systems were tested and compared against a reference case (standard roof). The test boxes were instrumented in order to measure temperature at a number of locations within the enclosed space as well as at layers of the roofing system. The purpose was to observe and analyze the effectiveness of the four test roof systems as compared to the standard roof. Analysis of the temperature data acquired from a 24 hour period in early summer 2005 provides clear indicators of the cooling effect of an irrigated planted roof system, while non-irrigated systems may turn out to be counter productive to the goal of reducing heat gain to the interior resulting from solar radiation on the roof.