Scientists have developed an all season smart roof coating that keeps homes warm during the winter and cool during the summer, without consuming natural gas or electricity. Research findings point to a ground-breaking technology that outperforms commercial coolroof systems in energy savings.
“Our all-season roof coating automatically switches from keeping you cool to warm, depending on outdoor air temperature. This is energy-free, emission-free air conditioning and heating, all in one device,” says Junqiao Wu, a faculty scientist in Berkeley Lab’s Materials Sciences Division and a UC Berkeley professor of materials science and engineering who led the study.
Today’s cool roof systems, such as reflective coatings, membranes, shingles, or tiles, have light-colored or darker “cool-colored” surfaces that cool homes by reflecting sunlight. These systems also emit some of the absorbed solar heat as thermal-infrared radiation; in this
natural process known as radiative cooling, thermal-infrared light is radiated away from the surface.
The problem with many coolroof systems is that they continue to radiate heat in the winter, which drives up heating costs, Wu explains. “Our new material—called a temperature-adaptive radiative coating or TARC—can enable energy savings by automatically turning off the radiative cooling in the winter, overcoming the problem of overcooling,” he informs. TARC is the first roof coating that automatically switches between cooling in hot weather to warming in cold weather by regulating its rate of radiative
cooling.
The researchers plan to develop TARC prototypes on a larger scale to further test its performance as a practical roof coating. Wu said that TARC may also have potential as a thermally protective coating to prolong battery life in smartphones and laptops, and shield satellites and cars from extremely high or low temperatures. It could also be used to make temperature-regulating fabric for tents, greenhouse coverings, and even hats and jackets.
