Radiant Solar Heat
Radiant heat from the sun or from a radiant heater travels in a straight line to warm cooler objects-roofs, walls, people-rather than the air. Those objects absorb the heat and may re-radiate it to other cooler surfaces. Though air temperature may be chilly, you can still feel warm with radiant heating.
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Source:http://www.hometips.com/hyhw/comfort/38comf.html