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CONSIDERING RADIANT HEAT?

Thanks to advances in the heated floor industry, you can install hardwood floors over radiant heat - with confidence. That means you can enjoy the natural beauty of oak, ash, cherry, maple, hickory, walnut and other fine hardwoods and the comfort and efficiency of radiant heating. 

The York family chose cherry floors and radiant heat for the recent 1,500-square-foot expansion of their 250-year-old farmhouse in central New Jersey. "I like warmth under my feet," Susan York says. "If my feet are warm, I'm comfortable."

York has allergies and was eager to avoid some of the dust blown about by a traditional forced-air heating system. The cherry floors and radiant heating system were chosen for the new great room, kitchen, dining room and office in the colonial-style home in Asbury, NJ. York believes the choice will boost her home's resale value. 

"I think buyers today are more concerned about the quality of the air inside the house," she says. 

As early as 60 AD, the Romans discovered one way to heat an enclosed space is to introduce heat below the floor surface and let it radiate upward into the structure. 

Millennia later, radiant heating is more energy-efficient than conventional forced-air heating systems. Some manufacturers say their radiant heating systems will cut energy bills by 20 to 40 percent by avoiding the heat loss associated with forced-air systems. In most buildings, heat loss is greatest in the top half of the rooms and that's where heat is concentrated with forced air heating systems.

How Radiant Heat Works

Experienced installers of radiant-heat systems and hardwood floors work together to choose the system that best suits your needs. Electric systems use thin electric mats that work much like electric blankets. They often are used to heat small rooms like kitchens, bathrooms and entryways. Larger rooms often justify the more costly initial expense of installing a hydronic system, which involves heating water that runs through plastic tubes under the floor. Hydronic systems can be powered by gas, oil, electricity or solar energy. 

Radiant heat systems use a three-stage process to convey heated water to its destination.

  • A water heating system - comprising a standard boiler, water heater, geothermal heat pump or solar panels - warms the water.
  • A series of controls then pumps the heated water through a tubing network that is installed in the subfloor.
  • As the warm water moves through the tubing network, it releases its energy and returns to the boiler system to be reheated. This makes for smooth and gentle temperature variations.

Hydronic radiant heat systems can be installed in just one room or throughout a new or existing home. A plumbing and heating contractor typically performs the work in conjunction with a flooring installer. Most radiant heat system manufacturers will provide the names of contractors in a given area.

The maximum surface temperature of a wood floor is 85 degrees. Make sure your installer chooses a control strategy that assures this limit will not be exceeded, and gradually takes the floor through temperature changes.

Prices vary widely with the size of the room and type and quality of equipment. Costs could range from $3 to $10 per square foot plus installation. Robert Starr -- president of Radiantec, a radiant-heat system manufacturer founded in 1979 in Lyndonville, Vt. – estimates a system large enough to heat a 2,500-square-foot home would run about $5,000, excluding installation costs.

Natural hardwoods warm quickly and are cozy for bare feet because they conduct heat more efficiently than thick, padded carpets. Solid hardwood or engineered wood floors work fine with today’s high-tech radiant heat systems – whether on subfloors or concrete slabs. You can add inlays to new or existing wood floors over radiant heat and you also can paint and stencil the floors.

What about tropical woods?

The Radiant Panel Association, a trade organization for the radiant heating industry, warns against pioneering the use of a wood with little information on its dimensional stability. If you’re importing a tropical or exotic wood, you must pay close attention to the source and age of the wood as well as the method used in drying it. Quick drying creates stresses that can affect the wood later as it expands and contracts.

Which hardwood floors work best?

Extensive laboratory testing by Launstein Hardwood Floors in Mason, Mich., found that American hardwoods – including cherry, oak, ash, maple, hickory and walnut – are good choices for radiant-heat flooring.

For best results, use narrow boards, preferably not wider than 3 inches. Narrow boards will better accommodate wood’s expansion and contraction across a floor.

Consider using quarter-sawn wood for planks wider than 3 inches, regardless of species, for enhanced dimensional stability.

The Launstein testing found that quarter-sawn planks up to 7 inches across (when properly installed) can work well with radiant heat systems.

The testing also found that hardwood flooring that is three-eighths of an inch thick conducts heat better than thicker floors and resists gapping.

Installation Tips

Wood naturally expands and contracts to reach balance with the relative humidity of its surroundings. That’s why it’s important to avoid installing wood flooring when moisture levels typically rise sharply, especially during painting or the installation of sheet rock. When radiant heat is installed in concrete, mortar beds or gypsum cement, operate the heating system until these are completely dry before topping with wood floors. This can take several weeks.

Before hardwood floor installation, operate the heating system until the relative humidity in the space stabilizes to the average level expected for seasonal conditions in the area in which the wood floor will be installed. For example, if the space is expected to average 30 percent relative humidity in the winter and 50 percent in the summer, the average would be 40 percent. In especially dry regions like the American Southwest, a humidifier may be recommended, according to Roger Rohr, owner of Maxrohr, Inc., a radiant heat system installer in Rogersville, MO. Likewise, a dehumidifier may be called for in especially humid climates. 

Experienced flooring installers will ensure that the wood floor’s moisture content is appropriate for your area. A 6 to 8 percent moisture content is average in most parts of the country.

Care and maintenance

Caring for a hardwood floor with radiant heat is no different than caring for any other hardwood floor. Radiant heat systems also typically have no effect on refinishing guidelines. (It is, however, always best to check with the finish manufacturer.)

Article courtesy of the American Hardwood Information Center.