Economic Comparison of White, Green, and Black Flat Roofs in the United States

TitleEconomic Comparison of White, Green, and Black Flat Roofs in the United States
Publication TypeJournal Article
Year of Publication2014
AuthorsJulian Sproul, Man-Pun Wan, Benjamin H Mandel, Arthur H Rosenfeld
JournalEnergy and Buildings
Date Published3/2014
KeywordsBuilding codes, energy efficiency, Green roofs, Life-cycle cost analysis (LCCA), Stormwater management, urban heat island, White roofs

White and “green” (vegetated) roofs have begun replacing conventional black (dark-colored) roofs to mitigate the adverse effects of dark impervious urban surfaces. This paper presents an economic perspective on roof color choice using a 50-year life-cycle cost analysis (LCCA). We find that relative to black roofs, white roofs provide a 50-year net savings (NS) of $25/m2 ($2.40/ft2) and green roofs have a negative NS of $71/m2 ($6.60/ft2). Despite lasting at least twice as long as white or black roofs, green roofs cannot compensate for their installation cost premium. However, while the 50-year NS of white roofs compared to green roofs is $96/m2 ($8.90/ft2), the annualized cost premium is just $3.20/m2 -year ($0.30/ft2 -year). This annual difference is sufficiently small that the choice between a white and green roof should be based on preferences of the building owner. Owners concerned with global warming should choose white roofs, which are three times more effective than green roofs at cooling the globe. Owners concerned with local environmental benefits should choose green roofs, which offer built-in stormwater management and a “natural” urban landscape esthetic. We strongly recommend building code policies that phase out dark-colored roofs in warm climates to protect against their adverse public health externalities.