Installing Radiant Floor Heat

By: Tim Snyder (Page 3 of 4)

Photograph by Ralph Masullo

Secure the mat. Plywood or cement backerboard will work as a substrate for the heating cable. Staple into the plastic mat, not into the cable.

Trowel on the mastic. The thin profile of the cable and mat allows the cable to be easily embedded in the thinset application.

Lay the tile. Any type of tile can be installed. Complete the grout work and your floor is done.

Hydronic Tubing in a Thin Slab Over Wood Framing
This approach is for new construction and major remodeling. Floor framing must be adequate to support the additional weight of masonry and the water pumped through the tubing.

Hydronic tubing directly under hardwood flooring. This approach does raise the floor level about 1 in., but if installed properly with nailers between the tubing it will not harm the hardwood flooring above it. The 3/4-in. layer of hardwood radiates heat to the room.

Hydronic Tubing Directly Under Hardwood Flooring
This approach does raise the floor level about 1 inch, but if installed properly with nailers between the tubing it will not harm the hardwood flooring above it. The 3/4-inch layer of hardwood radiates heat to the room.

Hydronic Tubing in the Joist Spaces
If you have access to joist bays beneath the floor, you can install tubing against the bottom of the subfloor for radiant heat. Insulation beneath the tubing is essential. This is the only hydronic system that doesn't require substantial remodeling.

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Whole-House Radiant Heating

Hydronic radiant floors are heated by warm water pumped through plastic tubing. Other components in a typical hydronic system include a boiler or water heater, a circulation pump, a manifold of valves to control water distribution, and a thermostat to control temperature.

Due to size and complexity, most hydronic systems are installed by plumbers and/or HVAC contractors. The cost for an entire heating system ranges between $6 and $12 per square foot — two to three times the cost of other heating systems.

However, a hydronic system offers substantial operational savings when used throughout the house, or at least over an entire level. At this scale, you can save around one-third over what you'd pay to heat by forced air.

Carpet, tile, and vinyl flooring can go down over a hydronic masonry floor, although some efficiency is lost if you install a carpet pad. Tubing can also go down beneath a wood floor; it gets installed directly under the finish flooring or fastened to the underside of the subfloor, between joists (see illustrations). The joist-space option can work well in retrofit applications, provided you have access beneath the floor you want to heat.