Spending time outside during a heatwave can be sweaty, uncomfortable and even unhealthy, but scientists have developed an innovation that they say could provide relief: clothing that physically cools the body.
Researchers at the University of Massachusetts Amherst have developed a flexible, chalk-based coating that can be added to fabrics. During tests in the scorching summer heat, they found that it reduced the temperature underneath clothes by up to 8 degrees Fahrenheit compared to the air and by up to 15 degrees compared to untreated fabrics.
The innovation is one of a growing effort to turn people’s clothing into a tool against extreme heat, which is intensifying as humans continue to burn fossil fuels that are warming the planet. The heat is the deadliest type of extreme weather, causing heat exhaustion and even heat stroke, a potentially fatal disease in which the body loses the ability to cool itself.
The UMass researchers say they wanted to develop a way to cool fabric using an environmentally benign material. Inspired by traditional limestone-based plasters used to cool homes in hot climates, they coated the fabric tiles with particles of calcium carbonate, the main component of limestone and chalk.
The coating can both reflect solar energy back into the atmosphere and allow the wearer’s natural body heat to escape, according to a new study presented to the American Chemical Society this month and currently under peer review.
“We start with your cotton T-shirt… and apply this coating to one or both sides of the fabric,” Trisha L. Andrew, a chemist and materials scientist at UMass, told CNN. “The coating is completely at the surface level. It does not penetrate or alter the cotton fibers,” she added.
Scientists say the coating can be applied to almost any fabric on the market and is machine washable.
“Without any power input, we can reduce the temperature a person feels,” Evan Patamia, a graduate student at UMass who worked on the innovation, said in a statement. “This could be a valuable resource for people struggling to stay cool in extremely hot environments.”
Cooling fabrics aren’t a new invention, but according to a 2023 scientific review of cooling fabric research, past designs often featured rigid structures, complicated manufacturing processes, and electrical components, making them uncomfortable and expensive to wear.
The UMass project is part of a growing body of research investigating cheaper, more comfortable and more scalable alternatives as the threat of extreme heat grows around the world.
Scientists at RMIT University in Melbourne, Australia, used tiny particles called nanodiamonds to coat cotton fabrics, achieving a temperature reduction of up to 3 degrees Celsius (5.4 degrees Fahrenheit) compared to untreated cotton.
While this may not seem like a big deal, “it makes a difference in terms of comfort and health impacts in the long term, and in practical terms it can be the difference between keeping your air conditioning off or on,” Shadi Houshyar, senior lecturer and project leader at RMIT, said in a statement.
RMIT University research has found that using cooling fabrics can save 20 to 30 per cent of energy by reducing the use of air conditioning, a cooling medium that is a major polluter for the climate.
Nanodiamonds may sound expensive, but researchers say they are not the same as diamonds used in jewelry. “They are actually cheap to make,” Houshyar said.
There are still improvements to be made, he added. For example, they found that the efficiency of the nanodiamond fabric decreased after the fabric was washed several times.
Houshyar told CNN that the nanodiamonds work similarly to the limestone particles used by UMass. He said the principle of these studies is the same, using nanoparticles to draw heat away from the body.
Houshyar, who has been researching protective gear for more than a decade, said the manufacturing process used by UMass is promising, but they need to figure out how to scale it and keep costs low.
Cooling fabrics need to be affordable, he said. “If the cost is three times the cost of regular fabric, there won’t be enough for everyone to use.” Those most vulnerable to extreme heat and with the least access to cooling technologies are often the poorest people.
As more products enter the market, “there’s a lot of opportunity in this space to scale this to make it available to everyone,” Houshyar added.
UMass’ Andrew said his team has so far been limited by the size of their lab equipment, but through a new startup company they aim to launch a pilot production, producing sheets of treated fabric that are 5 feet wide and 300 feet long.
Raw material costs for the coating are “low to manageable,” Andrew said, but admitted the overall price would increase slightly due to the application process by which the coating is applied to the fabric.
If it proves possible to scale up production of affordable cooling fabrics, some researchers say their benefits could extend far beyond clothing.
Scientists at the University of Chicago hope that cooling fabrics made from materials like silver nanowires and wool could also be used to cool buildings and cars. In tests conducted under Arizona’s fierce sun, they found that the fabric stayed 16 degrees Fahrenheit cooler than commercial silk, a fabric often used in summer clothing.
Scientists say making cooling fabric more widely available could reduce air conditioning costs and climate impact. “Our civilization actually uses about 10% to 15% of total energy to feel comfortable everywhere we go,” Po-Chun Hsu, a professor of molecular engineering at the University of Chicago and a study author, said in a statement.
While combating extreme heat means rapidly reducing the burning of fossil fuels, deadly heatwaves are already here and some scientists believe these cooling fabrics could play a useful role as more people are exposed to temperatures their bodies find difficult to tolerate.
“Personal cooling textiles hold great promise in combating the heat-related impacts of climate change,” Xueping Zhang, a professor specializing in personal thermal-humidity management at Donghua University in China and one of the authors of a scientific review of cooling fabrics for 2023, told CNN.
“They can provide localized cooling to specific parts of the body with high accuracy,” he added, and can be adapted to different environments.
He sees a large-scale role for cooling fabrics — and soon. “With advances in materials and technology, personal cooling textiles will be available to the general public in the near future.”
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