How Does Radiant Floor Heating Work?

Quiet, efficient, cost-effective radiant heat is the ultimate in comfy warmth.

By: John Riha
Underfloor heating

Underfloor heating

Underfloor heating sistem- pipes, instalation, orange base

Radiant floor heating keeps rooms warm, doesn’t make any noise and it’s energy efficient. You can heat all of your house or supplement just a room or two.

With a radiant heat floor, the warmth rises evenly from below, so the temperature of the room is uniform from top to bottom — and your tootsies never get cold. It’s an especially nice feature in bathrooms.

Also, there’s no blowing air like with forced air systems. That means less stirred up dust and allergens.

Radiant floor heating is more expensive than conventional forced air systems, but over time saves money due to better efficiency — there aren’t any ducts to leak air and waste energy.

You can’t cool your house with radiant heat, so you’ll need a separate system for air conditioning when the weather warms up.

There are two basic types of radiant floor heating systems: electric and hot water.

Electric radiant floor heating uses electric resistance cables to produce heat. The most popular style features cables embedded in thin mats that can be installed under tile, stone, engineered wood, and laminate floors. Electric heating mats are good for retrofits.

The mats are connected to a thermostat controller where you can select temperature settings or set up a timer so floors are warm and welcoming in the morning. Some types are certified safe for use inside showers, too.

Electric radiant floor mats can’t be cut to fit around vanities and drains—you have to order the pieces from a manufacturer and put them together like a jigsaw puzzle. A solution is to install full-size mats just in high-traffic, open areas.

Some manufacturers make heating mats designed to be stapled between floor joists so you can add radiant floor heat from below without having to remove existing flooring. Insulation is then installed under the mats to keep the heat from dissipating downward.

Experienced do-it-yourselfers can handle electric radiant heat mat installations. Cost for the mats, connectors and controllers range from $5 to $7 per square foot. Add $3 to $5 per square foot if you’d rather hire a pro.

Electric single wire installations are an alternative to mats. They have a single, continuous, insulated wire that’s snaked around metal clips attached to the subfloor. That lets you customize the heating layout and put it exactly where you need it.

The single wire system is designed to be embedded in mortar with a finish flooring material installed over the mortar bed.

Hot water radiant systems, also called hydronic heating, use heated water circulating through PEX (cross-linked polyethylene) tubing. The tubing is embedded in mortar or in extra thick plywood subfloor panels that have pre-cut channels for holding the tubing in place. The plywood method can’t be used under nail-down flooring like hardwood.

Hydronic systems are attached to a hot water heater, a pump that circulates the water, and a thermostat to regulate room temperature. The system is closed, meaning it doesn’t connect to the hot water heater and system you use every day for washing, cooking and bathing.

Hydronic heating systems can also be used between floor joists under existing floors. That makes them good for renovations, but they aren’t recommended for DIY installation. You’ll pay $6 to $16 per square foot for a professionally installed system.

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