About Radiant In-Floor Water Heat

Radiant in-floor heating works differently than forced-air systems because radiant heat warms everything in the room, including you. Forced air systems tend to lose some efficiency through ductwork and through heat lost through cracks and gaps in a home. While forced air may leave hot and cold spots in rooms, radiant systems tend to heat in more uniform layers that many people find more comfortable.

  1. Types

    • There are two types of radiant systems: electric and hydronic. Electric systems consist of cables run under the floor and between joists or on slabs of concrete. Electric systems are not considered very cost-effective for entire homes because the cost of electricity is relatively expensive compared to other energy sources. Electric is used to retrofit single rooms, like bathrooms.

      According to the U.S. Department of Energy, hydronic systems are "the most popular and cost-effective radiant heating systems for heating-dominated climates." Hydronic systems circulate heated water through heavy-grade plastic tubing, often from the home's hot water heater, to provide radiant heat.


    • Unlike forced-air systems, radiant heat does not require any ductwork. Radiant in-floor heating is quiet, efficient and tends to retain warmth at a lower level inside the home, cooling as the home's convection takes air upward toward the ceiling. Thermostats can be turned down a few degrees with radiant heat because warmth is maintained closer to floor level. Hydronic systems can use most any heating source available--electric, gas, solar, wood, oil--to warm the water that circulates through the system.


    • Wet installations embed plastic tubing into a concrete slab or into a thin layer of concrete. Dry installations can be made by placing the tubing on top of or underneath subflooring. Dry installs can also be made by sandwiching the tubing between layers of flooring.


    • The type of flooring used in the home can make a difference in how well radiant systems work. Most types of flooring work well, even hardwood. Carpet may be an issue, especially if it's heavy carpet and uses a thick underlayment. This Old House plumbing and heating expert Richard Trethewey says, "If the floor is too well insulated, radiant heating really doesn't make sense. It's like putting a sweater over a radiator."

      Radiant systems are for heating only. A separate air conditioning system still needs to be maintained for warm weather.


    • Costs for a professional installation and materials can be pricey, anywhere from $6 to $15 per square foot depending on the type of installation (wet or dry), whether installation is on a brand new home or an existing one, and what part of the country you live in. Much of the cost is in labor, so several companies are now packaging do-it-yourself radiant heating systems with costs around 75 percent lower if the homeowner is willing to tackle the installation. ThisOldHouse.com estimates that radiant in-floor heating can be up to 30 percent more efficient than forced air, so a significant savings can be realized over time.

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  • Photo Credit Modern asian inspired hallway with bamboo floors image by MAXFX from Fotolia.com

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