As global temperatures continue to rise, so will the cost of keeping us cool. A building technique that’s thousands of years old might help.

Buildings are responsible for 40 percent of total energy use in the United States, including 75 percent of all electricity use, and produce 35 percent of the nation’s total carbon emissions, according to the US National Renewable Energy Laboratory.

“Building design has long-term consequences, not only with the building’s operation costs, but for the environment,” says Omar Al-Hassawi, assistant professor in Washington State University’s School of Design and Construction.

Growing up in Iraq, Al-Hassawi experienced how people cooled their homes without air-conditioning or electricity, often using similar techniques as ancient Egyptians for their buildings.

Black and white profile shot of Omar Al-Hassawi
Courtesy Omar Al-Hassawi / Linkedin

One method uses an architectural element called a wind tower to create a cross breeze, which cools the air as it passes down through the tower and into the home. Some of these towers also trap dry heat by using a water source at the base. The water evaporates as the hot air passes over it, reducing the air’s temperature through an effect called evaporative cooling.

Al-Hassawi realized he could improve upon these ancient techniques to help architectural students design more energy-efficient buildings.

“If we design buildings that perform better to begin with, before we rely on mechanical systems of cooling, we reduce energy consumption and in turn reduce greenhouse gas emissions,” Al-Hassawi says.

Al-Hassawi experiments with different tower designs in a climate-controlled test chamber housed inside a 60-square-foot, solar-powered shipping container on the WSU Pullman campus.

His work focuses on developing a multistage passive and hybrid down-draft cooling tower that can cool homes better than the traditional wind tower. By adding cooling coils at the top of the tower in addition to the evaporative cooling source at the bottom, the cooling effect is enough to rival a standard air-conditioning system without consuming nearly as much energy.

“The rise in demand for cooling is expected to grow about three times between now and 2050,” Al-Hassawi says. “We can’t keep designing these big glass boxes.”

Line drawing of two cooling towersTo measure the performance of down-draft cooling towers, Al-Hassawi arranged sensors to record air velocity, water flow, and temperatures inside and outside the tower. (Illustration courtesy Omar Al-Hassawi)