Philadelphia rooftop coating program reduces indoor heat by half

A program in Philadelphia, United States, using reflective white coatings on rooftops has successfully reduced the perceived heat inside homes by half. The initiative, which focused on low-income elderly residents, utilized materials with high solar radiation reflectivity rather than conventional white paint.

Data from the U.S. Environmental Protection Agency (EPA) indicates that the intervention reduced thermal gain through roofs by nearly 80%. Monitoring of 35 properties showed that roof temperatures dropped between 2.2°C and 2.8°C during the hottest days of the year. In upper-floor bedrooms lacking air conditioning, ambient air temperatures decreased by approximately 1°C.

The Philadelphia Cool Homes Project also reported an average annual energy saving of 560 kWh per household for climate control. Following these results, the City of Philadelphia resumed the strategy in late 2025 in partnership with the Energy Coordinating Agency, providing free coatings to 62 homes in the Strawberry Mansion neighborhood.