If you're going to test the limits聽of solar-heating efficiency, you might as well do it聽in one of the coldest places in North America:聽Fairbanks, Alaska.
Bruno and Judith Grunau鈥檚 has six solar thermal panels that drink聽in sunlight and send the heat to a 2,500-gallon underground tank. That hot water then travels through coils underneath the floor to warm the house, while two-foot-thick walls and triple-pane windows ensure the heat stays inside. When the mercury drops below freezing (it can reach negative聽30聽degrees in Fairbanks),聽the couple relies on an ultra-efficient, wood-burning masonry heater for an extra bump.
$狈础,听