measured 73% cooling savings and 5% heating penalty using cool fluorocarbon coatings on the roof of an industrial building located in Oss, Netherlands. In London, the optimum roof reflectivity for achieving energy savings was 0.6–0.7. All these studies in different climates around the world show that reflective roofs result in energy savings and reduced surface and indoor air temperatures, depending on climatic conditions and building characteristics. The cooling benefits and improvements in indoor thermal conditions for different climates (e.g., New York City, California cities, London, UK, and various locations in Greece, Italy, Spain, and France) have been the focus of recent research. Most of these studies are summarized in an excellent review by Santamouris. Several studies evaluated the impact of reflective roofs (i.e., with reflectivity higher than 50% for aged samples) on the cooling potential for buildings, neighborhoods, and even entire cities. Decision makers should consider building type, climatic conditions, roof insulation levels, and durability performance, along with roof reflectivity, when assessing the overall potential benefits of cool roofs.
The results show that (i) roof reflectivity is equally important to roof insulation in warm climates (ii) for low-rise offices and schools, the benefits of reflective roofs vs dark-colored roofs are clear for all US climatic zones, with higher savings in warm climates (iii) for big-box-retail buildings, reflective roofs perform better except for cold climate zones 7–8 (iv) dark-colored, mechanically attached roofs achieve slightly better performance than reflective roofs in mixed and cold climates. EnergyPlus was used to model three building types (retail, office, and school buildings) for the 16 most climate-representative locations in the US using typical reflectivity and insulation values.
This paper presents a comprehensive simulation study to evaluate the combined impact of roof reflectivity, insulation level, and construction type (adhered vs attached) on annual energy demand and energy costs in the United States, for different buildings and climate zones. While it is well-known that cool roofs can efficiently reduce cooling demand in buildings, their overall energy performance in mixed and cold climates has been a topic of debate.
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