Every morning, thousands of construction workers in Qatar start their day by soaking their uniforms in water. The two-minute ritual kickstarts an important process: When the workers are toiling outside — often at summer temperatures above 120F (48C) — their uniforms can cool skin temperature by as much as 8C (14F), for up to seven hours.

The uniforms are made by British startup Techniche International, which brands them as StayQool suits. Constructed from an outer layer of specially designed mesh, plus a waterproof inside layer, the suits absorb and remove heat through evaporation. They’re also adjustable: Workers can add or remove a cooling collar or wrist cuff as needed.

Techniche isn’t alone in seeing opportunity in apparel designed to beat the heat. With 2023 on track to be the hottest year on record, a number of startups are exploring new technologies and textiles for keeping people cool. In the US, work is underway to commercialize wearable technology that mimics air-conditioning, while scientists in China are working on highly reflective fabric. With more heat and more heat waves expected in the years ahead, cooling is becoming a holy grail for garment makers.

"As climate change pushes temperatures in extreme directions, demand from consumers for cooling apparel is also increasing at a faster pace,” says Sophie Bakalar, a partner at venture firm Collaborative Fund, which invests in climate-friendly apparel startups. “This trend is likely to continue as the Global South industrializes further and consumers have greater disposable income to spend on comfort.”

Extreme heat isn’t just inconvenient — it’s bad for human health, and the economy. Heat stress is particularly dangerous for children and the elderly, and can exacerbate existing medical conditions. Productivity also takes a hit. In 2021, heat exposure nixed 470 million potential labor hours globally in agriculture, construction, manufacturing and the service industry, according to data compiled by The Lancet. In the US, President Joe Biden has said heat waves cost the country $100 billion annually.

Research shows that heat waves are likely to become more frequent in coming decades. For companies like Techniche, that’s a recipe for growth. Today, the startup sells vests, hats, neck bands and other garments with built-in cooling technology to companies and individual customers in nearly 30 countries. Last year, it booked revenue of almost £7 million ($8.8 million), compared with £150,000 in 2014, when Techniche launched cooling baseball caps as its first commercial product.

“The market is growing enormously,” says co-founder and managing director James Russell.

The company is now developing a cooling vest that will come equipped with smart sensors capable of monitoring workers’ biometrics and predicting when they might be at risk of heat stress. It’s also working on gear that can absorb heat using phase-change materials, originally developed by NASA to help astronauts maintain a consistent body temperature in space.

On the other side of the world from Techniche’s London office, Renkun Chen, a professor of University of California at San Diego, is working on the same problem. Except Chen is leveraging his background in mechanical engineering to design clothes that come with air-conditioning.

Just as conventional air-conditioning units keep a space cool by transferring heat outside of it, Chen has crafted palm-sized thermoelectric devices that react to a preferred temperature set by the user. The devices are powered by rechargeable lithium-ion batteries, and are small and flexible enough to be embedded in clothing. They offer a maximum reduction in skin temperature of 10C.

“Our climate has already changed and this is irreversible,” Chen says. While cutting carbon emissions is vital, he says, “we also have to find ways to adapt to it, as more extremely hot days will surely come.”

Chen says his research team has already partnered with a California-based startup to commercialize the technology. They still need to develop an automated production line that can manufacture the thermoelectric devices at scale, which would lower production costs from several thousand dollars for one shirt to closer to $200. In China, researchers from Zhejiang University, Huazhong University of Science and Technology and several other institutes are taking another approach: clothes that reflect solar heat. The scientists manipulated the structure of polyester using nanomaterials and a redesigned weaving technique, resulting in a material that reflects roughly 90% of the sun’s rays, according to a 2021 study published in Science. A conventional white cotton shirt reflects about 60% of sunlight.

The reflective polyester also radiates more infrared energy than regular fabrics, which reduces body temperature. According to the study, the material can stay as much as 5C cooler than midday ambient air temperatures, and as much as 10C cooler at night. While their work has yet to be commercialized, the study’s authors noted that their polyester is “readily compatible” with making garments.

Even with the variety of approaches, most of these cooling solutions face similar limitations, says Bakalar at Collaborative Fund.

The biggest of those is price, which will have to come down to make high-tech cooling gear accessible and appealing. Even at a production cost of $200 per shirt, Chen’s AC clothes would be prohibitively expensive for most. Russell says Techniche’s cooling suit is priced comparably to mid-end gear worn by construction workers in the US and Europe, but costs more than four times as much as similar workwear in the developing world.

Some cooling clothes come with other trade-offs. To work for eight hours, Chen’s AC gear is embedded with roughly 1.5 kilograms (3.3 pounds) of electronic components. Techniche’s cooling vest is 20% heavier than a conventional option. Then there’s the limited styles on offer, and lingering skepticism from would-be buyers.

“It’s worth noting there are no strict guardrails required to validate brand claims around cooling just yet,” Bakalar says.

All of these impediments are part of what make outdoor workers a good demographic to target: Cooling clothes are more necessity than novelty for them, and companies that employ such workers are inclined to foot the bill. Nearly 90% of Techniche’s revenue comes from sectors like construction and oil drilling, Russell says.

But today’s niche solutions could very well be tomorrow’s mainstream fashion. July was the hottest month ever recorded. Over time, entrepreneurs like Russell expect adoption of cooling clothes to spread from outdoor laborers to almost everyone.“There will come a time when people will need to wear cooling clothing with sensors in, just to walk across the street,” he says. “It’s not tomorrow. It’s not the next day. [But] it’s absolutely inevitable.”