Cool Pavements Lower Temperatures

The Heat Island Group's Mel Pomerantz (left) and Hashem Akbari measure the temperatures of pavements with various albedos.

The graphic above is a colorful demonstration of lower temperatures associated with pavements with higher albedos (reflectivities). Link to: Pavement Albedo The Heat Island Group's Mel Pomerantz and Hashem Akbari measured the temperatures of three pavements outside of our laboratory. The albedos were measured at the same time of day. The dark, fresh asphalt had an albedo of 0.05 and a temperature of 123°F (51°C). The lighter, aged asphalt had an albedo of 0.15 and a temperature of 115°F (46°C). A prototype asphalt coating was developed in collaboration with Reed & Graham, Inc., of San Jose, California. This coating had an albedo of 0.51 and a temperature of only 88°F (31°C)!

It should be noted that the cool prototype asphalt coating was not selected purely on the basis of its high albedo. Pomerantz tested several formulations of coatings and chose one that had the best combined properties of mechanical durability and reflectance, not just the highest reflectance. A coating must be more than a reflector; it must function under rigorous abuse. The chart below shows that Pomerantz had five other coatings with higher reflectances from which to select.

There were five prototype asphalt coatings with higher reflectances than the one chosen for the test shown in the photograph above. For reference, the binder--the compound which binds the asphalt together) has a solar reflectance of 5%, much lower than any of the coatings we considered. These coatings were provided by Reed & Graham, Inc., of San Jose, California.

In less than twenty years of normal maintenance, we estimate that all existing pavements could be replaced with pavements of higher albedo. Increasing the average pavement albedo in the Los Angeles area to 0.25 could save $90 million annually. Link to: The Cost of Hotter Pavements. Lower pavement temperatures also lead to longer lifetimes for the pavement, saving yet more money. Link to: Pavement Durability.

For an overview of some benefits of low-albedo (cooler) pavements, link to: "Benefits of Cooler Pavements"