Friday, Aug. 11, 2023 | 2 a.m.
Climate scientist Ronnen Levinson travels from his home in Berkeley, Calif., to Las Vegas three or four times a year on business, and he says he’s often befuddled when he opens the curtains in his hotel room.
More times than not, he’s in a room that overlooks a roof outfitted with air conditioning equipment, and the material covering the roof is dark-colored.
Levinson leads the Heat Island Group at Lawrence Berkeley National Laboratory, a group that works to cool buildings, cities and the planet by making roofs, pavements and cars cooler in the sun. When he sees a dark roof, he wonders why more resorts — or building owners in Las Vegas in general — don’t repaint them to a lighter color, even if only to save on electricity costs.
Levinson is an expert on urban heat islands, which form when cities are mostly made up of pavement and buildings that retain heat, driving temperatures higher than they’d otherwise reach with no greenery or shade.
Las Vegas is an urban heat island and is one of the fastest-warming cities in the country, second only to Reno, according to the environmental nonprofit Climate Central.
“The thing that drives the difference in the temperatures of the city’s surfaces, its pavements, its walls, its roofs, is sunlight,” Levinson said.
Most painted buildings cast a diffused reflection that only reflects some light that hits it, while a mirrorlike reflection reflects it all. Levinson said roughly speaking, half will be reflected back up at the sky and half will be reflected down.
“The half that goes down will strike other surfaces, like other walls, or the ground, or people,” he said.
He said that’s more reason that buildings should be painted light colors or with paints designed to keep the surfaces cool.
“When you’re on the Strip … you’re trying to make a building that’s attractive, so you don’t want something as unexciting as an off-white wall,” Levinson said. “But there’s also a lot of flat roof areas doing nothing but holding air conditioning equipment, so there’s a certain irony to all of this.”
As for those HVAC units, all of them vent heat into their outdoor surroundings. They raise the temperature further and force neighboring units to work harder and longer to maintain cool indoor temperatures, generating even more outside heat in an endless cycle.
A cool roof, on the other hand, reflects sunlight and efficiently emits any heat absorbed, reducing the amount of heat conducted into the building below. This, in turn, keeps the building cooler, according to the Cool Roof Rating Council, a nonprofit group that administers product rating programs for roofing and exterior wall products. Levinson is an ex-officio board member of the CCRC.
Las Vegas Strip architecture, with its range of styles and materials, and no shortage of tall glass buildings, isn’t the target for most cooling technologies, Levinson said.
“When we look at cool solutions, while I’m sure they’re applicable to some of the architecturally fancy buildings, mostly we’re looking at what you can do for the vast majority of homes and commercial buildings,” Levinson said.
Replacing a residential roof with a cool roof costs about as much as one made of conventional materials, Levinson said. Older and less efficiently insulated homes, especially, stand to benefit from a new roof, he said.
“It’s not that you should do it, I’m just saying it’s easier to do the cool wall,” Levinson said.
Las Vegas just endured the hottest July on record, and experts predict generally rising temperatures and more extreme weather events in the future. That outlook makes combating the urban heat island effect in Las Vegas even more important, experts agree.
Reducing the effects of heat islands would require sweeping infrastructure and construction changes but would result in instant improvement, Levinson said.
The addition of green spaces would also reduce the effects of heat islands, and in Las Vegas that extends beyond the Strip.
East Las Vegas, particularly, is lacking in green spaces that would help reduce the heat island effect, improve air quality and contribute to long-term health improvements, said Rico Ocampo, director of organizing for Make The Road Nevada, a nonprofit group that advocates for working-class immigrants
“We want our community leaders and those who represent us at the higher level to hear our concerns and invest in our communities, rather than divest from these critical resources like trees, parks and places for our community to rest,” said Ocampo, speaking to the Sun at Freedom Park, the only major park in East Las Vegas.
Adding more greenery is only part of the equation, Ocampo said. Community members have told Ocampo that more public transportation and more adequate shade at bus stops would also help, he said.
A 2022 National Oceanic and Atmospheric Administration-funded heat mapping study involved a group of 60 volunteers who spread out across Clark County to check the temperatures in different locations during the morning, afternoon and night.
The map produced from that data shows that elevated temperatures are worst in North Las Vegas, East Las Vegas and downtown, which can get up to 11 degrees hotter than other parts of the city. Steffen Lehmann, an architecture professor and urban heat expert at UNLV, said he came to Las Vegas five years ago to study the urban heat island effect after conducting studies in Asian, Australian and European cities.
“Governments have been extremely slow to put mitigation strategies for extreme heat in place because you can’t see it,” he said. “And there are many action plans, but very little action.”
He said combating the effect long term would mean rethinking urban design, balancing density with built-in green spaces and incorporating cool materials and paints.
“Higher densities are unavoidable, but we have to go to what I call ‘quality density,’ ” he said. “We have to accommodate the growth.”
He said urban heat islands have been forming across the American Southwest, from Palm Springs, Calif. to Albuquerque, N.M., to El Paso, Texas.
“It’s all suffering,” he said. “100 million people, 40 cities were affected by these extreme temperatures, and next year we’re going to speak about the same problem again. Same health concerns, very little will happen in one year, and we’ll have the same heat waves again next year. So, we have to start doing something about it.”
