“What sunscreen does is prevent the sun from
damaging the surface,” Murphy said. “The same
sort of effect is what we want to achieve with
cool pavement.”
The Environmental Protection Agency says
normal paving materials can reach temperatures
of 120 to 150 degrees Fahrenheit (48 to 67
Celsius) during peak summer and transfer
excess heat into the air. Lowering the surface
temperature can provide comfort and reduced
energy costs to residents sheltering from
extreme heat like the record levels reached
this year in Arizona, California, New Mexico
and Texas.
Phoenix set a U.S. record Oct. 14 for 144 days of
temperatures over 100 degrees (37.7 Celsius),
the most in a calendar year. The previous record
of 143 days was in 1989. The city in the Sonoran
Desert also set records this year for 50 days
of 110 degrees (43.3 Celsius) or more and the
hottest August since temperature tracking
began in 1896.
Heat island effect is a “major factor” in both day
and nighttime temperatures and a potential
health hazard, Arizona State Climatologist
Nancy Selover said, noting the particular risk to
those who cannot afford air conditioning and
homeless residents sleeping outside.
“When we stay hot at night — we had 29
mornings that had a temperature of 90 or higher
at sunrise this year — the day just gets hotter
from there,” Selover said in an email. “So the
maximum is likely to be a few degrees warmer
than it would be if the night had cooled.”