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Radiant floor heating, because of the large heating surface working at a relatively low temperature, is the best way to use active solar and geothermal (ground source heat pumps) in building heating. The staff of Solar Consultants has years of experience integrating solar input with space heating systems. We work with H1 licensed heating contractors, including Select Heating and Air, Bowman Mechanical, Evangelist Geothermal, and others, to design and coordinate these installations.

Characteristics of Radiant Heat

Radiant floor heating uses warm fluid (usually water) running through pipes imbedded 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 only needs to be about 90-110 degrees -- not boiler 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, not the coldest. (This is especially an asset in bathrooms, for people with poor circulation, and is a hit with the cat and dog.) 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.

PEX pipes ready for concrete pour
Radiant Heating in Basement

In the image on the left, foam board insulation, wire mesh, and polyethylene (PEX) pipe loops have been laid and secured, ready for the concrete floor pouring in this Enertia house near Wake Forest. Separate loops of pipes have already been placed in the basement walls before they were poured (their ends can be seen emerging from the walls) and attached to the plywood subfloor above. The basement walls and floor will be one zone (an area controlled by one thermostat, pump, and manifold unit) and the wood floor above will be another, which might run at a slightly different temperature.

In the photo below the interior walls and control joints have been marked so the pipes can be routed.

PEX pipe loops ready for concrete

Here is an example Radiant Slab Module for a 1000 sq. ft. basement in an Enertia house. The heat source in this case is an Aquastar 125BL propane-fired instantaneous water heater (not shown).

Radiant Heating Module

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