Can radiant heating be installed under our existing flooring?


Can radiant heating be installed under our existing flooring?

Asked by Ben Pinder, San Jose, CA

Can radiant floor heating be added after we've already installed new bamboo and tile flooring? We have a single-floor home with access to the crawlspace. Which is better: electric-heat pads or water-circulating pipes? How much will it cost to install? Will it save energy?

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Brad Hubbell's picture

Radiant heat can be added under your existing floor. In this situation, hydronic radiant heat (water circulating through pipes) would be easier to install than electric mat radiant heat.

  • Electric mat radiant heat is best when sandwiched between the subfloor and the finish material, be it wood, tile, or carpet.
  • Since your new flooring is already in place, hydronic radiant heat is a more practical choice. The tubes can be fastened to the underside of the subfloor with staples.
  • Then a radiant barrier can be installed below the tubes to ensure that the heat remains focused on the flooring and living space above.

A home of roughly 2,200 square feet should be able to run a radiant system off its water heater. But if your home is in the neighborhood of 3,000 square feet, be prepared to invest in a boiler. (The boiler can also serve as the hot water source for your home if you add a small domestic-water reserve tank.) If your roof has good southern exposure, solar panels can augment the energy required to heat and maintain the water in the system.

The benefits of radiant heat are many.

  • Radiant heating systems heat the mass of the floor, which not only retains the heat but also increases the comfort of the living spaces.
  • We typically sense temperature fluctuations through our feet, so we feel warm if the floor is warm, even when the air temperature is cold.
  • The system does react more slowly than a forced-air system to fluctuations in your desired indoor temperature. However, it takes less energy to maintain a certain temperature since water carries heat much more efficiently than air.
  • Another benefit is the ability to create multiple zones (areas heated by the system independently and at different temperature settings).

Radiant heating installations are usually followed by lower heating bills for two reasons: Thermostat settings can be lowered, and zoning can be tailored for the lifestyle of the inhabitants.

In your area, you might expect to pay between $17,000 and $23,000 for a radiant system in a 2,200-square-foot home, using a domestic water heater as the heat source.

  • This translates to roughly $8 to $12 per square foot.
  • Add more to this cost if the house is larger (over 2,500 square feet) and a separate boiler is needed.

For more information:

Radiantec's website provides helpful information for the do-it-yourselfer.

Thanks to Brent Farlie atWarm Floorsin Napa, Calif., for his assistance with this question.