Study finds Nashville Transportation’s ‘cool paving’ project could actually make you feel hotter

NASHVILLE, Tenn. (WSMV) - With temperatures hitting triple digits on Thursday, it can feel more than 15 degrees hotter in Nashville than other surrounding areas.

The city is considered a heat island, where concrete and asphalt trap heat and the Nashville Department of Transportation is trying to fix the issue by putting a new reflective paving on the road.

This gray reflective coating has only been applied to a test site along part of 5th Street in East Nashville for the Cool Pavement Pilot Program. NDOT Assistant Director Phillip Jones said they have been measuring the surface temperature three times per day for about six weeks now and found it is around 10 degrees cooler than normal pavement.

However, a study by Arizona State University, an area already using this sealant, found the cool pavement could actually make people feel hotter. Researchers said people can feel five degrees warmer than standing next to the regular pavement because the heat is being bounced back at them instead of absorbing into the road.

The study also found the air temperature six feet above the ground treated with the cool pavement was only 0.3 degrees lower during the day and 0.5 degrees lower at night.

“It may not affect us in the same way during the day, but it’s the late afternoons and the evenings when we will really see the effect of that,” Jones said. “Because where we have lost our tree canopy, and we have that which protects the asphalt from holding that heat longer into the afternoon and night, this will make it to where the air temperature actually gets cooler in the late afternoon and night. That is what we are hoping to research, and that is the effect we are looking for.”

Jones said less heat radiating from the pavement throughout the evening can help lower the strain on A/C units and save people money. He is not yet sure how this pavement will work in Nashville though because it has never been used in this humid of a climate.

The city got the test area of this sealant for free and has a contractor willing to spray it in other areas if they want to expand this pilot program, Jones said. NDOT has not yet gotten any bids on how much it would cost to cover the entire city.

Jones said it will take at least a year to fully understand how it works and holds up to the weather. NDOT is going to start a pilot on a similar product down the street from the current test area next month to compare its benefits.

Even if it only has a minor impact on cooling, Jones said NDOT will consider using the cool pavement as a sealant in place of normal fogging if it is durable and cost-effective.

“That is what we need to continue to evaluate,” Jones said. “The thing that I have not found any study on is in a humid area like this, we have not seen what the impact really is. We couldn’t have picked a better time to get it out and try this demo to where we can actually find out what is the result.”

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