Dear EarthTalk: How energy efficient (and comfortable) is underfloor heating, sometimes known as radiant heating?
— Marcy Dell, Boston, MA
Underfloor radiant heating involves under laying the floor with a hot element or tubing that transfers heat into the room via infrared radiation and convection, obviating the need for forced or blowing air.
According to the U.S. Department of Energy’s Energy Savers website, radiant heating has a number of advantages over other forms of heat distribution: “It is more efficient than baseboard heating and usually more efficient than forced-air heating because no energy is lost through ducts.” It is also flexible as it can run off of a variety of energy sources: Gas, oil, wood, solar and other sources or combinations thereof can feed radiant systems. And radiant heating is a good choice for those with severe allergies as no potentially irritating particles get blown around the room.
Several aspects of radiant heating make it more energy efficient. For starters, the uniform heat distribution over the entire surface of a floor heats the lower half of the room, enveloping inhabitants in warmth at a lower overall temperature—in some cases up to five degrees Fahrenheit cooler—than a conventional heating system. “Radiators and other forms of ‘point’ heating circulate heat inefficiently and hence need to run for longer periods to obtain comfort levels,” reports the Residential Energy Services Network (RESNet). “They draw cold air across the floor and send warm air up to the ceiling, where it then falls, heating the room from the top down, creating drafts and circulating dust and allergens.” RESNet adds that radiant systems transmit heat on average some 15 percent more efficiently than conventional radiators.
The efficiency gains can be magnified significantly with good insulation and a well-designed system. While tearing out old heating systems and/or replacing decent existing flooring might be overkill for the sake of moving to radiant heat, those embarking on new building projects or contemplating major renovations should certainly consider it. According to TLC Network’s Green Living Guide, there are two main types of radiant heating, electric and hydronic. In the former, heated wires installed in the floor radiate heat upward.
This type of radiant heat is most commonly used to retrofit a single room—especially a bathroom or kitchen—in an older house or building. Meanwhile, hydronic radiant heating, whereby heated water is forced through tubes under the floor, is more often designed into a new structure from the get-go, and is more energy efficient overall.
TLC points out that while radiant heat is definitely more efficient in smaller, snug homes with lower roofs, it might not always be the greenest solution in homes with bigger rooms: “In some scenarios it can be less energy efficient than forced-air heating.” TLC recommends consulting with a reputable heating contractor to see if radiant heating is a sensible way to go.
Of course, pairing a radiant heating system with an energy efficient EnergySTAR-approved programmable thermostat can indeed save households hundreds of dollars a year on home heating bills while keeping inhabitants warmer all year long. Many states offer financial incentives to upgrade home and commercial heating systems in ways that boost energy efficiency. Check out the free Database of State Incentives for Renewable Energy (DSIRE) to find out what kinds of tax rebates or other incentives might be available in your neck of the woods.