An update on the Cool Pavement Pilot Project

Since 2024, the City has been testing whether "cool pavements" can make urban areas cooler, safer and more comfortable during hot weather in Philadelphia. This project is part of the City's efforts to address extreme heat, especially in vulnerable communities where temperatures can be nearly 30°F warmer than others. One year later, the project is entering Phase Two.

What is the Cool Pavement pilot?

In summer 2024, through a partnership with CoolSeal by GuardTop, the Office of Sustainability and the Streets Department launched the Cool Pavement pilot.

The pilot is testing if changing pavement surface materials - from black asphalt to a light-colored, reflective sealant - can potentially lower air temperatures. The sealant absorbs less heat and reflects more sunlight than traditional dark pavement. When applied to roads, these "cool pavements" can be cooler during the day and give off less stored heat at night.

The pilot will test if cool pavements can help reduce the "urban heat island effect," where some areas get hotter and stay hotter than their surroundings. Urban heat islands often form in dense parts of the city with lots of dark-colored roads and surfaces, and few trees and plants. The City is working with researchers at the University of Pennsylvania's Composto Research Group and Thermal Architecture Lab to test:

• The potential cooling benefits of the sealant, measured in multiple ways (e.g. surface temperature, air temperature, mean radiant temperature).
• How the sealant holds up with routine use and cleaning.
• How the sealant holds up through Philadelphia's climate and environmental conditions. This includes through freeze and thaw cycles, and salting during icy weather.

Phase One

In 2024, the City applied one coat of CoolSeal sealant on a section of pavement in Hunting Park. After a year, researchers found:

• Compared to untreated dark asphalt, the coated pavement surface took longer to heat up. It stayed cooler from morning until afternoon.
• There did not appear to be a significant difference in the air temperatures above the coated pavement compared to dark asphalt.
• The new sealant's impact on lowering air temperatures was inconclusive and required further study.

What's next

The next phase of the pilot, which began in August 2025, will test the potential cooling benefits and durability of two coats of sealant on park pavement. The City is continuing to assess whether the new sealant can deliver lasting cooling benefits to create a safer and healthier environment for Philadelphians.