Impact of a Switchable Albedo Radiative Cooling Roof on Building Energy Performance

Radiative cooling roofs can reduce cooling demand and achieve subambient surface temperatures under sunlight, but their high solar reflectance can increase heating demand during cold periods. Switchable albedo radiative cooling roofs may mitigate this seasonal trade-off by switching between cooling and heating states. However, their annual building energy effects across different climates remain insufficiently quantified. This study evaluated a mechanically switchable albedo radiative cooling roof using a U.S. Department of Energy strip mall prototype in eight U.S. cities representing distinct climate zones. Four roof configurations were compared: a baseline roof, a traditional cool roof, a non-switchable radiative cooling roof, and a switchable albedo radiative cooling roof. A retrospective monthly state selection procedure was used to combine the results of two fixed-state annual simulations. The modeled coating, based on properties reported in the literature, changed from a solar reflectance of 0.93 under mechanical stretching to 0.05 under mechanical compression while maintaining high thermal emissivity. In climates dominated by cooling demand, the switchable albedo radiative cooling roofs and non-switchable radiative cooling roofs produced similar cooling benefits. In moderate and cold climates, switching avoided annual heating energy penalties while reducing annual cooling electricity use by 12.0–22.8% relative to the baseline. Under the adopted 2018 energy price assumptions, the switchable albedo radiative cooling roof reduced annual cooling and heating expenditure by 1.7–8.4% in moderate and cold climates. The main benefit of switching was therefore the mitigation of seasonal overcooling while retaining radiative cooling benefits in climates with appreciable heating demand.