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A guide to underfloor heating

You decided to install a ceramic tile floor in your bathroom, but you live in a part of the world where it gets incredibly cold during the winter. Now, when you walk across that floor, your toes curl up from the chill and you are seriously considering major back surgery to eliminate the sensation of cold that travels up your spine.

There is a solution: You need to add a component to the mix known as a 'warm floor.' A warm floor is a type of radiant heating system that is reasonably simple to install and whose addition can substantially improve your personal comfort on chilly mornings.

A radiant heating system uses a series of electric cables or small tubes of hot water embedded in a concrete floor; or embedded in the mortar or mastic beneath a tiled floor, beneath carpet; or attached to the underside of a wooden subfloor.

Instead of heating air and circulating it through the house, radiant heat warms objects such as tile, carpet, hardwood and furniture.

Tile is the preferred surface as it radiates the generated heat better than the other types of flooring we mentioned.

Folks who have radiant heat swear by it. They say it is by far the most even and comfortable type of heat.

Radiant heating companies claim that less energy is needed to transfer heat directly to people, rather than to fill the entire room with heated air as a forced-air furnace does. We feel that their statement is debatable. Truth is, radiant heating can cost at least 50 percent more than forced air heating.

We agree that radiant heating has its advantages and that it is comfortable and efficient, but there are major drawbacks. Radiant heating cannot be accessed easily for repair. Because it usually is built into the floor, repair or replacement can in many situations require removal of structural parts of the home - a very expensive proposition.

Also, massive use of electricity in most parts of the country is simply not as energy-efficient or as cost-effective as gas-fired heating.

So, keep in mind that although we like radiant heating for special uses, like warming a tile bathroom floor, we feel that much consideration would have to be given before installing it throughout one's home.

A warm floor for a small bathroom with an inexpensive thermostat (not recommended) is about $200. Keep in mind this is exclusive of any other work such as the flooring itself. Warm floors for bathrooms can cost as much as $2,000 - again, exclusive of any floor-finishing work. Most folks can figure costs coming somewhere in the middle.

Warm-floor dealers are usually found through flooring stores. You can also find warm-floor contractors by typing 'warm floor' into your computer's search engine. Warm-floor manufacturing companies list their dealers all over the country. Type in your ZIP code and you're there.

Electric heating cables can be embedded in the mortar or mastic under tiled floors. Some manufacturers offer the product in a portable mat that can be quickly and easily cut to fit the irregular shaped room, a useful installation option.

Also, such mats are great for renters because they are portable. Who would have thought that people could take warm tootsies with them during a house move?

By the way, the temperature of the floor in a given room is controlled by a wall-mount thermostat. In the old days these thermostats were nothing more than an on/off switch. Today they have been replaced with highly sophisticated digital controls that improve comfort and reduce operating cost.

For a mortar floor, electric cables are most versatile. First, double-headed nails are driven into the wooden subfloor to a uniform depth (where the nail heads are about three-fourths of an inch above the floor and about 6 inches apart in two directions - think tic-tac-toe here).

The cable is placed alongside the double-head of each nail and zip-ties are used to hold the cable to each nail. The cable is woven back and forth so that rows of wire, spaced and held at 6-inch increments, cover the entire floor.

Mortar is poured to a depth of about 1 inch, completely covering the wire and the nails. The beginning end of the wire and the ending end of the wire have to end up at the same location and travel up inside the wall to the thermostat. It's that simple.

Tile is then laid over the mortar bed as it normally would be without any special consideration for the warm floor hidden beneath.