The best ways to cool a home—without turning on the AC
Summary
For decades, architects and homeowners just assumed air conditioning would keep people comfortable. Now they are looking to the past to stay cool.
As the world warms, it’s getting harder—and more expensive—to beat the heat. But architects, designers and homeowners are looking for ways to keep homes comfortable without air conditioning, or at least with less reliance on it.
For years, the idea of turning off the AC was unthinkable. Since home air conditioning became widespread in the U.S. in the 1960s, architects paid little heed to maximizing or minimizing a house’s exposure to the sun or prevailing winds.
“We could build the same house anywhere on Earth, taking the house completely out of context," says Graham Irwin, principal architect at California-based Essential Habitat Architecture.
His firm is one of many that design or renovate homes with today’s focus on energy conservation in mind—creating so-called passive houses, which meet a series of energy-efficient standards to be more climate friendly. “We normally see about an 80% reduction in energy use in the houses we work on," he says.
Throwing shade
One of the key features of a passive house is that it is heavily insulated and sealed up tight to keep warmth inside during the winter and cool air inside during the summer. Passive houses also incorporate passive cooling techniques, using architectural and natural methods to keep a house from heating up by blocking the sun and enhancing ventilation.
Take the home called the Midori Haus in Santa Cruz, Calif.—a passive house that has no air conditioning. When Chie Kawahara and her husband decided to buy the rundown, nearly century-old bungalow in 2010, they had to undertake a major remodeling. They decided to make it as green as possible. Kawahara met Irwin of Essential Habitat at a passive-house conference and engaged him to help with the project.
They replaced the siding and blew massive amounts of insulation into the walls and under the roof to plug every gap. Old, leaky windows and doors gave way to modern ones, and a state-of-the-art ventilation system was installed to regulate the climate inside the house.
Although Santa Cruz has a relatively mild climate, summers are getting hotter, and the temperature can exceed 100 degrees at times. But, despite the lack of air conditioning, the temperature inside the house rarely exceeds 72 degrees, even during extreme temperature spikes.
Of course, not everyone can afford the kind of overhaul that was done to this house. But one element of the renovation, while still expensive, illustrates a simpler step that many homeowners could take—shading the windows.
In the Midori Haus, that involved adding two porches to the house with retractable awnings that can be pulled out to keep the sun from shining on the lower part of the house and into the windows beneath them. Covered porches were once far more widespread than they are today, especially in the hotter regions in the U.S.
But porches aren’t needed to shade a home’s windows. “Another tradition that’s been completely lost in the U.S. is awnings and shutters" on windows throughout a house, says Stephen Atkinson, an architect in Palo Alto, Calif. “It is such a common-sense thing to do: Protect all the glass surfaces from the sun because of the greenhouse effect"—windows allowing sunlight in and trapping the heat it produces in the building.
Other traditional ways of shading are also making a comeback in home design. Recessed windows, a key feature of adobe houses in the Southwest and the Middle East, are being integrated in designs of some new passive houses. By setting the window back, the building’s facade casts shade onto the glass.
A more elaborate system of shading was designed by architect Lawrence Scarpa for the Cherokee Studios in Los Angeles, a mixed-use collection of lofts that integrate a variety of passive cooling features. The building has a double facade, with a shell of perforated anodized-aluminum panels that can be maneuvered to block out the sun or let more light in.
A cool breeze
Ventilation is also key. Atkinson, the Palo Alto architect, has tapped into his Louisiana heritage to design homes raised on stilts, a technique that not only prevents flooding but also allows cooling air to circulate beneath them. Corey Saft, professor of architecture and design at the University of Louisiana at Lafayette, is working on a design that echoes the traditional Louisiana dogtrot house with its use of a covered breezeway running between two homes, providing shade and ventilation.
Fans can also help ventilate a home. Older buildings used to have whole-house fans under the roof that drew hot air out of the building while drawing in cooler air from outside through open windows. Most of those fans were sealed up when air conditioners became common, but they are starting to make a comeback. Architects are also building homes with higher ceilings and high vents or windows that can release hot air as it rises naturally.
Another cooling design element is a courtyard. With shade from trees and awnings, and the cooling impact of a fountain, a courtyard can become a source of cooler air that enters the home.
How a house is oriented also is important. In hot climates around the world, builders traditionally would take into account the direction of the sun, prevailing winds and any nearby bodies of water in positioning homes to minimize the warming effect of sunlight. “If you orient a building properly, you can reduce the heat gain by 50%," Scarpa says.
Marco Petruzzi, chief executive of Dovetail Furniture, a wholesale home-furnishings company in the Los Angeles area, had a house designed and built by Scarpa’s firm, Brooks + Scarpa. The house’s cooling features include solar panels that double as an overhanging roof for shade, and windows positioned high to release heat from the building.
There is no air conditioning in the living quarters downstairs, only in the bedrooms for those times when Petruzzi wants to close the windows to block out the noise of a nearby highway. When the windows are open, warm air escapes through them and is replaced by cool air drawn from downstairs by that airflow.
Scarpa says architects are increasingly looking toward the past to understand how homes were designed and built before air conditioning.
“Many old houses were built well," he says. “We can’t solve everything with design, but can make it tolerable 90% of the year."
William Boston is a writer in Berlin. He can be reached at reports@wsj.com.
