Radiation occurs with electromagnetic waves which transfer heat without the need for the presence of matter. Stefan-Boltzmann 's equation for heat radiation. When air is free to flow under a house, any hot air will flow out and cooler air will flow under the floor. The earth cools off at night much more quickly when the weather is clear than when cloudy. When there are no clouds heat is radiated into space thus cooling the earth.
Clouds reflect radiation back.
An electric fan does not cool air. If feels cooler only in the airstream because the moving air increases the rate of evapouration from the skin. A piece of wood lying in the sun absorbs more heat than a piece of shiny metal. The wood, however, feels less hot than the metal when you pick it up. A mountain climber wears down clothing 3.8 cm thick whose total surface area is 1.8 m 2 .