Exterior, Concrete Siding Material, Flat RoofLine, and House Building Type “The sun rises behind the house and heats up the concrete mass during the morning, and [comes] through the front of the house in the afternoon; if need be the radiant energy warms up the house when temperatures drop in the evening,” says Thorsteinsson. Thanks to the thoughtful process, the couple was able to leave out the air-conditioning, and the house’s under-floor radiant heating system has turned out to be almost superfluous.  Photo 1 of 5 in Building Green in Santa Monica