Radiation is energy transferred by infrared waves through space. Examples: heat from the sun or warmth from a campfire. Radiation penetrates solid surfaces such as shingles, wood and concrete. During the winter, typically 50-75% of heat loss in buildings is a result of radiation and 93% of the heat gain in the summer is radiant.
In the summer once a building’s walls, roof and attic have reached their capacity for holding heat, the heat is then radiated to the cooler interior area of the building. In the winter, the opposite occurs. The heat from the inside of the building moves towards the cold air outside the building.