The color of your house matters beyond aesthetics. An extensive body of research shows that painting buildings white (which reflects heat) can make them cooler, and painting them black (which absorbs heat) can make them warmer. This is the reason why most houses in Greece are white, and many housesacross Scandinavia are black. But what about the rest of the world, where temperatures often shift with the seasons?Industrial designer Joe Doucet has developed what he calls a climate-adaptive paint that can change colors based on the temperature outside. The patent-pending formula, which is known as thermochromic paint, follows the same principle as 90s mood rings. Except instead of jewelry changing color, its the entire facade of a building. If the temperature outside is below 77F, the building will be black. If its above 77F, it will turn white.The formula can be mixed with other tints, so if you want a blue house, it would simply look light blue in the summer and dark blue in the winter. Its phenomenal to think about the built environment changing with the seasons as nature does, says Doucet, who estimates that painting a building with this climate-adaptive paint could save an average of 20 to 30% on energy costs.The power of paintMany cities have turned to paint to alleviate urban problems like the heat island effect. In 2019, teams across Senegal, Bangladesh, Mexico, and Indonesia painted a total of 250,000 small household rooftops with white reflective pain as part of the Million Cool Roofs Challenge. In 2022, the city of L.A. covered 1 million square feet of streets and sidewalks in Pacoima, a low-income neighborhood, with solar reflective paint. Surfaces cooled instantly by 10 to 12F, and a year in, studies showed that the ambient temperatures throughout the entire neighborhood had dropped by up to 3.5F.[Image: courtesy Joe Doucet and Partners]A climate-adaptive paint could make a difference for houses and apartment buildings, but also large industrial facilities like climate-controlled farms and warehouses that would otherwise turn to AC or heating to maintain a desired temperature. It costs to heat and cool a large structure so anything you can do mitigate that cost makes sense commercially as well, says Richard Hinzel, partner and managing director at Joe Doucet and Partners.Doucet first had the idea for a climate-adaptive paint while renovating his own home in Chappaqua, New York. I put off what color it should be because I wanted to have an understanding of what color did in terms of energy use, he recalls. The designer, who recently gave wind turbines a much-needed design makeover, built two scale models of his house, with the same kind of insulation material he used in the actual house. He painted the first model in black and the second one in white. For a year, he measured the surface outside and inside both models, and found that, in high seasons like summer and winter, temperatures between the two varied by as much as 13F. More specifically, in the summer, the white house was 12F cooler inside than the black house, while in the winter, the black house was 7F warmer inside. He says the opposite was also true. The black house was 13F warmer inside in the summer, while the white house was 8F colder in the winter. [Image: courtesy Joe Doucet and Partners]Doucet obtained these measurements from a scale model, not a full-sized house, but he notes the only difference between the two would be the time it takes for each space to heat or cool. A smaller pan heats up and cools down faster than a larger one, but it does not get hotter or colder, he says by way of example.At the end of the experiment, it occurred to him that the answer to his original questionwhat color to paint his housewas to paint it black in the winter and white in the summer. But that wasnt a practical solution.The more practical solutiona paint that can be both at oncetook two years to develop and about 100 more models to get the formula right. The team used commercially available latex house paint as a base, then mixed in their own proprietary formula. But crafting a formula that can sustain the transition from light to dark without degradingand therefore ending up greyproved difficult.If youve ever had transition glasses that got stuck on dark and never returned to clear, you understand the problem. If the paint degrades too fast and you have to repaint your house every month, then nobody will buy it.The first few formulas were degrading too fast, but the team eventually concocted a secret sauce that helps the paint last at least one year with zero degradation. This number reflects how long Doucet has been testing the paint in his studio. The final number could be even higheror it could not.The paint is yet to undergo rigorous lab tests, so many unknowns remain. Were not starting a paint company, says Doucet. Instead, his team wants to license the formula to paint manufacturers who would then take the climate-adaptive paint to the finishing line and launch it themselves.If the idea resonates and paint companies jump on the bandwagon, they will have to develop a competitive product that is both durable and pricedaccordingly. For now, Doucet estimates that the climate-adaptive paint will cost about 3 to 5 times more than a standard gallon of paintthough he says youd quickly make that back in energy savings. Im confident that if theres a positive response, this could do very well on the market, he says.In the meantime, Doucet finished renovating his house and opted for black. I couldnt wait, he says with a laugh.