Heat radiation
Also: thermal radiation
Electromagnetic radiation emitted from a material body by virtue of (and characteristic of) its temperature.
(At "room temperature", this radiation falls into the infrared (IR) range.)
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.