Longman Dictionary of Contemporary English
underfloor heating
noun
EXAMPLES FROM CORPUS
▪ Available in 2 m widths, it can be seam welded to cover large areas and is especially good over underfloor heating.
▪ It is fully double glazed, and ventilation plus an underfloor heating system means it can be used all year round.
▪ The substantial remains of the cavalry fort include a bath house showing the sophisticated workings of the underfloor heating system.
▪ With the underfloor heating at a bare minimum, it gave out considerably more heat than wood, and I loathed it.
Wikipedia
Underfloor heating
Underfloor heating and cooling is a form of central heating and cooling which achieves indoor climate control for thermal comfort using conduction, radiation and convection. The terms radiant heating and radiant cooling are commonly used to describe this approach because radiation is responsible for a significant portion of the resulting thermal comfort but this usage is technically correct only when radiation composes more than 50% of the heat exchange between the floor and the rest of the space.