Cool Roof - Case Study

Case Study

In a 2001 federal study, the Lawrence Berkeley National Laboratory (LBNL) measured and calculated the reduction in peak energy demand associated with a cool roof’s surface reflectance. LBNL found that, compared to the original black rubber roofing membrane on the Texas retail building studied, a retrofitted vinyl membrane delivered an average decrease of 24 °C (75.2 °F) in surface temperature, an 11% decrease in aggregate air conditioning energy consumption, and a corresponding 14% drop in peak hour demand. The average daily summertime temperature of the black roof surface was 75 °C (167 °F), but once retrofitted with a white reflective surface, it measured 52 °C (126 °F). Without considering any tax benefits or other utility charges, annual energy expenditures were reduced by $7,200 or $0.07/square foot.

Instruments measured weather conditions on the roof, temperatures inside the building and throughout the roof layers, and air conditioning and total building power consumption. Measurements were taken with the original black rubber roofing membrane and then after replacement with a white vinyl roof with the same insulation and HVAC systems in place.