Energy photo

Researchers at ETH-Zurich are borrowing from biology to cool buildings in a novel way: by making them “sweat.” They’ve developed a permeable polymer mat that can be spread across rooftops to absorb moisture like a sponge when it rains, locking it inside. But when heated to a certain temperature by the sun the material becomes hydrophobic and pushes the water out. Just as humans expel heat from the body by imparting it to sweat on our skins that then vaporizes to carry the heat away, so would these “sweating” buildings remain passively cool by imparting their heat to water evaporating into the atmosphere, shaving up to 60 percent off air conditioning loads.