Hydronic Heating – Floor Heating
Hydronic floor heating is accomplished by circulating water through tubes embedded in a masonry floor (wet system), or either sandwiched between two pieces of plywood or attached directly to the underside of the sublfoor (dry system). Floor heating can also be accomplished with electric resistance coils embedded into or under the floor surface. This would be a form of radiant heating, but, since no liquid is involved, it is not a hydronic heating system.
Floor heating is virtually invisible and does not take up the wall space that other types of heating equipment may require. Various types of PEX or other plastic-type piping is used due to its very long lifespan. Full lengths of pipe without any joints eliminate maintenance of the piping loop.
Water in the system can be heated by a gas, oil or electric resistance boiler or by a water heater. Due to its efficiency, natural gas is most often used. Water or ground source heat pumps are also an option. Condensing boilers are a very efficient choice for hydronic floor heating because the boiler temperature can be set to the relatively lower level needed for floor heating. Underfloor heating systems can run at a temperature as low as 95°F.
Radiant heat travels in all directions, unlike heated air, which tends to rise, so insulation is needed to direct the heat upwards to the floor. A large area such as a floor heated to a lower temperature is capable of transferring as much heat as a small surface at a high temperature.
In a single-purpose system, the boiler or water heater provide hot water for only floor heating in contrast to the dual-purpose system where one unit performs two functions—hot water for the radiant floor system and for domestic use.