Radiation

Radiation is the transmission and emission of infra-red energy in the form of electromagnetic waves when heat is transferred from a warm body to a colder one without heating the substance it passes through.

Bodies that absorb thermal rays from the sun are also radiating bodies. That means much of the heat absorbed in daytime are radiated at night, unless cloud cover reduces radiation. When roof cladding radiates its heat, it is known as 'night sky radiation'. (See Night Sky Radiation)