Adept Materials’ dehumidifying paint was inspired by trees and semiconductors

The steam that condenses on your bathroom mirror may not seem like a big deal, but for architects and builders, it can be an enormous headache.

“Moisture control is something that is a major pain point,” Derek Stein, founder and CEO of Adept Materials. “If you just google your favorite home builders’ name and then ‘lawsuit,’ you’ll see lots of examples.”

Homes and offices used to “breathe” through cracks and crevices that were missed during construction. But in the quest for greater energy efficiency, builders are sealing things up. Tight buildings keep indoor temperatures more consistent, but they can also trap humidity.

“Essentially, buildings are being made more and more like beer coolers. It’s great for energy efficiency, but it’s pretty clear that people don’t like living in beer coolers,” Stein said. “And it leads to all of these other problems, like moisture damage.”

Running a dehumidifier is one option, but they can be noisy and expensive. Stein, who used to be a physics professor at Brown University, came up with another: a two-material system that helps homes self-regulate their internal humidity. His inspiration? Trees and semiconductor diodes.

Trees and other plants regulate their temperature in part by transpiring water through small pores in their leaves. If they get too hot, they open those pores and let more water evaporate, just like sweat cools our skin. When the temperature drops, they can close the pores to slow the rate of transpiration. Stein figured that if he could find a way to similarly absorb and disperse water vapor at the right times, he could make buildings more comfortable and energy efficient.

Lots of materials can do that, but they’re not very smart about where they disperse the moisture. Without something to help the moisture move in the desired direction — outside of a wall cavity, for example — mold and rot could result.

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That’s where the diode came in. As a physicist, Stein was intimately familiar with their operation. In a diode, electrons can flow freely in one direction but are resisted in the other. Essentially, they operate like a one-way door.

What he devised was a system of two materials. One acts as a sponge to absorb water vapor and release it over time. The other is a more typical weather-resistive barrier, which helps block air flow while allowing water vapor to pass through it. Stein’s sponge layer helps serve as traffic cop: When mounted to an exterior wall, the spongy layer will pull moisture away out of the house through the inward-facing barrier. It stays there until the sun warms the outside of the wall and evaporates the moisture. 

Builders buy a lot of weather-resistive barriers, about $14 billion worth in 2022, according to Global Market Insights. But the construction industry tends to be cautious when it comes to new technologies, in part because fixing any problem they cause can be costly. “In construction, the valley of death is usually deep and wide,” Stein said, referring to the gap between developing a product and actually getting customers to buy it.

To traverse the valley, Adept is designing its building wrap to look and feel like the old stuff. “One of the big barriers to adoption is that something looks and feels different,” he said. “People are resistant to change.”

While Adept refines its water-resistive barriers, the startup will sell another product, a paint and primer system aimed at bathrooms. The primer serves as the barrier layer, while the paint serves as the sponge. As humidity rises in the bathroom, the super-absorbent paint draws in moisture and doesn’t release it until the humidity in the bathroom drops. 

To test the paint’s performance, Adept built a bathroom-sized room and boiled water to raise the humidity. The paint managed to keep the humidity down by 14% compared with conventional paint, Stein said. Adept’s paint and primer will hit the market early next year.

The startup recently raised a $4 million seed round to help bring the paint to market while continuing development of the water-resistive barrier. The round was led by D.R. Horton with PulteGroup participating. Both are among the largest homebuilders in the U.S.

“As a startup company, you want to pilot runs and stuff like that, but people might not give you the time of day,” Stein said. “But if the biggest homebuilder in the U.S. says this is interesting to us, then it moves the needle.”