Air conditioning allows for comfortable temperatures within buildings in a hot climate, although it carries costs that go beyond the price tag of electricity. Air-conditioning systems use a lot of power and emit heat and gases that contribute to the greenhouse effect, worsening the heat waves they are meant to mitigate. That is why materials scientists have been moving toward passive approaches that cool spaces without using energy. An experiment carried out in 2025 by researchers from Penn State and Dalian University of Technology of China demonstrates the extent to which this idea has been realized.
A box built from sintered PMMA maintained a 15-degree gap from the outdoor air
