Cement normally soaks up heat from the sun,and that in turn makes our buildings hotter. So we crank up the A/C.That's a major problem for the climate: as the planet warms, and A/C use grows, the energy used for air-conditioning is expected to triple by the middle of the century. Air conditioners, ironically, are perpetuating extreme heat as they contribute to climate change. But they're not the only way to keep buildings cool.