White houses are often boring, but they might just save the planet. As USA Today reports, Purdue University researchers have developed an ultra-white paint (it just earned a Guinness World Record) that reflects 98.1 percent of solar radiation while outputting infrared heat. As this leaves the surface cooler than the environment (regular paint warms the surface), it could effectively replace air conditioning in some cases — it produces a cooling power of 10kW for a 1,000sq. ft. roof, or more than a typical house AC unit.
There are existing paints made to reflect heat, but they reflect no more than 90 percent of sunlight and don’t cool surfaces. The team didn’t have much breathing room, either — an even whiter paint might have compromised it.
The trick was to use a high ratio of barium sulfate, a compound you often see in cosmetics and photo paper, in varying particle sizes. The wider range of sizes helps scatter more of the light spectrum and thus reflect more sunlight.