Zigzag walls could help buildings beat the heat

Here’s a twist: Adding zigzags to walls could help cool an overheated building, even as global temperatures rise.

Researchers devised a new, electricity-free design for vertical walls that can cool the building more efficiently than conventional walls. These zigzags, just a few centimeters wide, can reduce daily average wall temperatures by a couple degrees Celsius, the team reports August 9 in Nexus.

Buildings currently consume about 40 percent of global energy and account for over a third of global carbon dioxide emissions, a large fraction of which comes from energy-intensive air conditioning (SN: 10/24/23). So researchers have hunted for ways to reduce that energy load with designs that can redirect more and more of the sun’s energy.

Most “radiative cooling” designs involve roofs designed to take in and then emit the sun’s energy at infrared wavelengths that radiate through Earth’s atmosphere and into space. Such roofs can be bedecked with plants, painted white to better reflect sunlight, or coated in materials that are both highly reflective and highly emissive (SN: 2/6/23).

Vertical walls are trickier to cool, says materials scientist Yuan Yang of Columbia University. That’s because they don’t just face out toward space, but simultaneously absorb heat from the ground. An efficient radiative cooling design must account for both effects.

Hence: zigzag walls. Yang’s team hypothesized that by corrugating the vertical surface and coating the facets with different materials — more reflective materials facing downward and more emissive materials facing upward — the wall could absorb less heat than a conventional straight wall.

Simulations comparing how much heat conventional and zigzag walls gained from the ground during a hot day supported that hypothesis. The average difference in wall temperature was about 2.3 degrees, a difference that rose to 3.1 degrees during the hottest part of the day. The team found a similar difference when they tested a miniature backyard version of their design in summer 2022 in New Jersey.

How zigzags affected a wall’s temperature

The goal was to design something that would be commercially appealing, Yang says. Corrugated walls already exist, he notes, and the design is easy to manufacture and scale up, perhaps finding a way for consumers to zig when the climate zags.