Radiant floor heating uses warm fluid (usually water) running through pipes embedded in or attached to the floor to heat space.
It is a good complement to passive solar design because both systems work well with building on an insulated slab, providing mass for passive heat storage and a convenient and protected location for the pipes.
The larger the radiating surface, the lower the temperature difference needed to transfer heat. This means the water does not need to be boiling hot for floor heating to work. This makes radiant floor heating a good complement to active solar water heating.
A backup heat source is installed for times when solar heat has been insufficient. Typically, a gas-fired tank-type water heater, instantaneous water heater, geothermal heat pump, or boiler is used, but the backup can be any type of heater, using whatever fuel is locally available. The system is usually coordinated with the domestic water heating, with a heat exchanger separating potable water and the heating system.
Heat from the floor warms all the mass in your rooms, giving every surface an inviting sensation that you can feel. The floor becomes the warmest surface in the room. The floor surface temperature can be adjusted to adapt to any floor covering.
Radiant floor heating does not blow air from one room to another, so less heat is lost from air infiltration and through windows or walls. In fact, you will not need to use ceiling fans during the winter because radiated heat does not rise up and stratify at the ceiling as does hot air. It is very quiet and the equipment (module mounted on a wall) takes up little space.