Environment & Climate
Phoenix cool pavement initiative lowers surface temperatures but raises daytime air heat
A study of reflective road coatings in Phoenix shows cooler pavement and lower nighttime air temperatures, alongside higher daytime heat for pedestrians.
The short version
- Phoenix's Cool Pavement Program, initiated in 2020 with Arizona State University, uses reflective coatings to mitigate urban heat island effects.
- Tests show treated road surface temperatures dropped by up to 12 degrees Fahrenheit, but reflected heat raised daytime air temperatures near the surface by approximately 5.5 degrees Fahrenheit.
- Nighttime air temperatures above treated surfaces showed slight cooling, indicating reduced heat retention by asphalt.
Key facts
- Phoenix and Arizona State University initiated the Cool Pavement Program in 2020 to test reflective coatings such as CoolSeal on road and parking lot surfaces.[Jalopnik]
- Reflective coatings lowered pavement surface temperatures by 12 degrees Fahrenheit at noon and 10.5 degrees Fahrenheit in the afternoon compared to untreated pavement.[Jalopnik]
- Temperatures below the surface of treated roads averaged 4.8 degrees Fahrenheit cooler than untreated asphalt.[Jalopnik]
- The reflective coating increased daytime surface air temperatures by about 5.5 degrees Fahrenheit due to reflected heat.[Jalopnik]
- After sunset, air temperatures six feet above treated surfaces were 0.5 degrees Fahrenheit cooler than above untreated roads.[Jalopnik]
What remains uncertain
- It remains uncertain whether city officials will deem the trade-off of higher daytime pedestrian air exposure acceptable relative to infrastructure longevity and lower nighttime heat storage.[Jalopnik]