“These two directions require different properties for cool walls,” says Qilong Cheng, a postdoctoral researcher at Purdue University who worked on the study as a graduate student at Columbia University. “So we have this two-surface zigzag design, with one surface facing the sky and the other facing the ground.”
The angles, looking a little like the sawtooth roofs of factory rooms, can shave 5.5° Fahrenheit off average indoor temperatures.
Radiation coming up from the ground is reduced or deflected by one material, while heat from the sun is reflected with ultra-white paint.
