Although temperatures are pushed to unheard-of extremes, my un-air-conditioned apartment stayed tolerable. The tile (瓷砖) floors seemed to emanate coolness. The greenery surrounding my windows blocked direct sunlight and helped bring down the temperature of the outside air. I didn't have a temperature meter, but I guess the temperature inside never got above 80 degrees.
"You saw for yourself the power of passive cooling," buildings scientist Alexandra Rempel told me. "It really can be amazingly, amazingly effective." Rempel studies how to design buildings that can stay cool "passively". Passive cooling can help protect people without access to air conditioning and lighten the load on the electrical grid from those who do. It can also help reduce greenhouse gas emissions produced by burning fossil fuels for power.
It's important to understand why buildings get hot. During the day, heat comes from solar radiation—the sunlight that streams through windows and beats down on roofs and walls. At night, the big problem is environmental radiation—the energy releasing from concrete and any other surfaces that had been absorbing sunlight all day. Passive cooling is about effectively managing these sources of radiation. And timing is everything.
As soon as the sun rises, window shades should come down. Window glass is "one of the weakest links" in a building's defense against solar radiation, because it readily transmits heat. Having vegetation around your building can prevent the walls from heating up as well. Trees not only provide shade, they can bring down the surrounding air temperature through a process called evaporative cooling (蒸发冷却)."Cool roofs"also make a big difference. Topping a building with light-colored, highly reflective materials prevents it from soaking up the sun's heat.
"If you can limit the amount of solar radiation your home absorbs during the day, you will have less environmental radiation to worry about once the sun sets. The techniques that helped my apartment beat the heat—shade, building materials, and strategic ventilation—can be used in almost any home," Rempel explained.
