New Roofing Material Keeps Buildings Cool Without AC

Cooling paper reflects the heat off of rooftops and out of your home.

Keeping homes cool without air conditioning.

(sommart sombutwanitkul /

Some people love hot summers. When the temperature soars during the summer, they enjoy the heat of the sun on their bodies and all the outdoor activities of the season. Other people like to beat the heat and stay cool in their air conditioned homes, offices, and cars.

Of course, AC also comes with a large price tag in terms of energy use and the environment. Wouldn’t it be great if you could cool your home with no electricity at all? Now, with a new invention, you soon may be able to.

Finding a way to cool without electricity is what Yi Zheng, an associate professor of mechanical and industrial engineering at Northeastern University in Boston, Massachusetts, set out to do when he created a sustainable material that can cool buildings without a cooling system according to a press release from the university.

The material that Zheng calls cooling paper works to reflect the solar rays away from buildings and also sucks the heat outside of the interiors. That’s because the natural fibers in the paper’s porous microstructure absorbs the heat and re-emits it away from buildings. It can be used on the roofs of homes and  commercial buildings as well as incorporated into building materials for new construction.

The idea for the invention actually came to Zheng when he saw a recycling bucket filled with used printed paper. He said in the press release that he thought to himself, How could we simply transform that waste material into some functional energy material, composite materials?”

So he used his own high-speed blender and made a pulp out of the waste paper and the material that is used to make Teflon and formed it into a water-repelling paper that can be used to coat buildings. Then Zheng and his team tested the cooling paper under different temperatures and humidity levels.

They found that the paper could reduce the temperature inside by as much as 10 degrees Fahrenheit, which can make a big difference on a hot day. “I was surprised when I obtained the same result,” Zheng said. “We thought there would be maybe 10 percent, 20 percent of loss, but no.”

Three-quarters of all homes in the US have air conditioners, according to The Hill, and these appliances release approximately 117 million tons of carbon dioxide into the air each year that contributes to global warming. The new invention could reduce carbon emissions as well as electrical use.

Another plus is that the material is recyclable because it can be reformed and still perform as well as the original.

This innovative way to cool buildings was featured in the American Chemical Society journal Applied Materials & Interfaces and Zheng won a national Science foundation CAREER Award grant in 2019 to conduct his research.

“The ultimate goal is to reduce global warming,” Zheng said in the press release. “The starting point is to reduce the use of carbon-based materials and also to reduce global warming.” His cooling paper could go a long way to making this happen.

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