Cool Pavement Pilot Program

Outcomes

The initial pilot project produced several key findings, including the following:

• The surface temperatures of asphalt surfaces treated with the cool pavement coating were consistently lower than non-treated asphalt concrete at all times of day. The cool pavement surface temperature was, on average, 2.4°F lower at sunrise, 12.0°F lower at noon and 10.5°F lower in the afternoons.
• Sub-surface temperatures beneath the cool pavement coating were 4.8°F lower, on average, than temperatures beneath untreated asphalt.
• The cool pavement-coated surfaces displayed around 33-38% solar reflectivity when the coating was first applied. 10 months post-installation, solar reflectivity ranged from 19-30% across the eight test neighborhoods. This decline in reflectivity leads to a less significant decrease in surface and sub-surface temperatures. Untreated asphalt, for comparison, absorbs more solar radiation and has a consistent reflectivity of 12%.
• Mean radiant temperature, which represents the average human’s total radiant heat exposure when walking on the treated surfaces, increased by an average of 5.5% due to higher surface reflectivity.

The second phase of the project explored the benefits of an updated pavement coating. Key findings from the second phase include:

• Cool pavement effectively reduces summer surface temperatures by up to 12° during the day compared to conventional aged pavement.
• Cool pavement may ultimately reduce long-term road maintenance needs and costs, which could yield substantiation economic and environmental benefits.
• Cool pavement impacts on air temperature currently appear to be small, but beneficial.