For most of human history, buildings were essentially net zero energy systems. Thick walls kept out cold and simple windows let in fresh air and daylight. Then came complex, expensive, energy-guzzling systems for air conditioning, ventilation, heating, and artificial lighting. Now buildings use 40% of all of the energy consumed in the U.S., and the rest of the world is beginning to follow similar patterns.
Could a new high-tech material help return some buildings to zero energy use, while retaining modern comforts? Researchers at the University of California-Berkeley have designed a new membrane that wraps around a building instead of walls, filled with micro-scale valves and lenses that open and close as they sense light, heat, and humidity. The facade works with no power at all—not even solar panels—and keeps the temperature comfortable and light bright inside.
"It began with the aim of being a skin that can breathe, similar to our skin, that can open and close its pores, to regulate the temperature, humidity, and light conditions," says architect Maria-Paz Gutierrez, whose research team is collaborating on the new material, called SABER, with bioengineer Luke Lee.
The researchers are working to make the material an ultra-low-cost solution for developing countries, where energy use is quickly skyrocketing. Though per-capita energy use is still highest in countries like the U.S. and Canada, the total amount of energy used in developing countries is already twice as large, and by 2050, will likely be at least five times bigger than developed countries.
"We focus more on technologies that are applicable for developing nations because that's where the big thrust of innovation in construction takes place," Gutierrez says. "We're looking at tropical regions, since that's where you have the largest population that requires strategies that are low cost."
Though the membrane doesn't actually cool the air, it makes buildings in hot, humid tropical countries more comfortable. "As we all know, when you augment natural ventilation, you augment human comfort without decreasing temperature," Gutierrez explains. "If you augment and enable evaporation, you can with the same temperature have a much higher threshold for comfort."
Because the facade can be scaled to any size, it could be used for anything from low-cost disaster shelters to huge stadiums. "If you're in Haiti after an earthquake and terribly hot, you're not going to be using an air conditioner even if you could get access to it," says Gutierrez. "That's out of the question. So this is a net zero cooling option."
The researchers have successfully tested a prototype embedded in a common building material, and are working on making the technology as cheap as possible so it can be manufactured and widely adopted. They're also working on a suite of other self-regulating materials for buildings.
"In some ways the reach of this, beyond the specific material itself, is also creating awareness of the critical opportunities that exist to develop self-regulating systems," Gutierrez says. "That's the fundamental difference between, for example, photovoltaics that follow the sun path or other types of systems that depend on mechanized activation—as efficient as they may be, they still require input. The idea here is to develop materials that are fully self-regulating."