Underfloor heating (UFH) is a form of heating in which the floor surface of a space is heated and this heat is then radiated (and convected) throughout the space to create comfortable thermal conditions. It has been used for thousands of years as a form of space heating, most notably by the Romans, whose hypocaust system consisted of a raised floor through which warm air and smoke were drawn to heat the floor before being discharged through flues.
Modern underfloor heating tends to use either electrical resistance elements or fluid-flowing, hydronic systems to heat the floor.

Underfloor heating systems tend to be low-temperature systems, as the heating surface covers a much larger area than conventional radiators which because of their relatively small size have to operate at a high temperature.
Underfloor heating can be installed on new-build projects, or retrofitted into existing spaces. It can be installed as the primary heating system or used to provide additional, localised heating in specific spaces such as bathrooms. It may be used in combination with renewable heat sources, thermal mass and night-time purging.

Systems can be modular or custom designed and installed, and will generally include insulation under the heat source to reduce heat loss.