- Coming next, house-sized deodorant sticks.
When the summer heat gets unbearable, you just turn on your air conditioner for near-instant relief. At least that’s what you do here in America.
In many places of the world, though, having an AC in your home is a luxury that very few people are privileged enough to have. Yet, in many of the same places, the weather is much hotter.
What can folks do to try and stay cool in the relentless heat? Well, they might soon be able to paint their houses with this new paint that keeps them cool through an innovative, strange, and a little gross method.
Basically, the paint cools houses by making them sweat.
The white paint reflects sunlight, but its most groundbreaking feature is that it traps moisture on its surface. This small amount of water siphons heat from the house as it evaporates — which is precisely what your sweat does to your skin.
But perhaps the best part is that the paint works entirely without consuming energy. It keeps your home’s temperature more tolerable and slashes your bills. What’s not to love?
What Came Before
In all fairness, cooling house paints aren’t anything new. Simply painting your house white helps keep it cooler through radiative cooling.
To give you a brief crash course in the physics of a cool home, white surfaces (like walls in this case) reflect sunlight. As more light bounces off, less heat energy gets transferred into the wall and the home stays cooler.
It’s simple, but it can be surprisingly effective. For a little while, at least.
Modern commercially available cooling house paints have two main issues. The first is that they don’t stay white very long.
The paints tend to yellow within a few years, which not only makes your house look gross, but also significantly reduces the cooling effect. Consequently, you end up repainting your house every few years, which doesn’t come cheap.
The second problem has to do with humidity. If the air is very humid, the ambient water vapor traps heat on the wall’s surface, preventing it from escaping with the reflected sunlight.
So, white house paint can be a good choice if you live somewhere hot and dry, like the desert of Arizona. But if your house is somewhere muggy and humid, like Singapore, it’s just not worth it.
Introducing: House Sweat
Unsurprisingly, the inventors of the new cooling paint come from Singapore. A research team from Nanyang Technological University, led by material scientist Li Hong, set out to develop a novel paint that could work even in their home country’s horrendous humidity.
Their work resulted in the new cement-based paint. Unlike current commercial paints, the new stuff relies on evaporative cooling in addition to radiative cooling.
The paint is white, so it still reflects sunlight away. However, it has a sweaty trick up its sleeve to deal with Singapore’s climate.
When painted on a wall, the paint forms a porous surface that traps small amounts of moisture. Having water sit on your walls might sound like begging for a mold problem, but in this case, the moisture doesn’t stick around for long.
The sun’s heat causes the trapped water to evaporate. As it does so, it transfers heat away from the wall and into the air.
If that sounds familiar, it’s probably because it’s how your body keeps cool. The paint basically makes your home sweat like you do.
Kind of gross, but if it keeps you comfortable in your home…
You Sweat Hard When You Work Hard
But does the paint keep you comfortable? Well, it certainly helps.
According to the research team, the white paint reflects 88-92% of all sunlight that reaches it. Of the heat that it inevitably absorbs, it dispels 95% by sweating it away.
The moisture on the paint’s surface also helps it last longer. By preventing the paint from drying and cracking in the sun, it remains functional (and good-looking) for longer than current commercial cooling paints.
Case in point, the researchers painted three houses — one with regular white paint, one with a commercial cooling paint, and one with their new miracle paint. In Singapore’s climate, the first two paints yellowed within two years, but the new one stayed pearly white.
And what about the financial side of things? The paint’s developers said it helped the house cut its cooling-related energy costs by 30-40%.
Considering our energy bills this summer, we’d pick a sweaty house over shoveling money to the power company in a heartbeat.