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AmerCable Incorporated

Articles - Flooring

Affordable efficient comfort for cold feet: a radiant heat primer.

Along with all the good news about radiant heat--the romance of bare feet on warm floors and the energy efficiency of the systems--there's been no shortage of debate about what floor coverings work, or don't work, with radiant. We've all heard the horror stories of inadequate heat through carpet, or dehydrated wide plank flooring with quarter-inch gaps.

The truth is that if the radiant heat professional knows what type of flooring will be chosen and installed, almost any type of floor covering can be applied over radiant heat. At the most basic level, the purpose of any heating system is to keep us warm. The unexpectedly luxurious feel of radiant heat keeps ns warm, but not by heating us. We don't need the heat! It keeps us warm by controlling the heat loss from our bodies.

Objects around us don't have their own energy source and since their surface temperature is less than our skin's 85 degrees, our bodies actually try to heat up these objects. Comfort is tied to the amount of heat we lose. If we lose too much heat, we feel uncomfortably cold. That's especially true when it comes to our feet--they're down there, connecting us with the products of your profession, and those tile and stone floors can be cold!

Radiant floor heating works by using water-filled tubes or electric heating elements to warm the mass of a floor. The surface of the floor then gently emits energy to all the objects in the room, making them--and your feet--cozy warm.

Radiant heat is ideal for either new construction or retro-fit. Market demand is high because of its great comfort, the highest energy efficiency available--typically, a 25 percent improvement over forced air--and with no air grates, radiators or baseboard to factor in, there's no interference with room function or furniture layout. Radiant heat systems also can operate on any number of energy sources.

Today, there are "also many ways to deliver radiant heat to existing and new floors. These systems also offer snow-melting options for safe access to a home.

Here's to Comfort

With radiant, the floor becomes the warmest surface in your room, not the coldest. Surprisingly, those surfaces most uncomfortable without radiant heat--stone, tile and hardwood--become the most comfortable with radiant heat because they transfer the heat so well.

Allergy sufferers love radiant heat. In many instances, the sources of irritation in homes and at work stem from vigorously circulated, forced-airborne dust and allergens. These problems are eliminated with radiant heat. And, anyone with arthritis or poor circulation will enjoy the warmth of radiant.

Lower Operating Costs

Whether hydronic or electric, radiant floor heat costs less to operate than any other form of heat. Because radiant floors offer more comfort at lower thermostat settings, most people find that they're comfortable at lower room temperatures. A key source of residential heat loss is energy that escapes from the building as cooler air infiltrates the home. Because of the lower air temperatures in a radiantly heated home, and the lack of forced circulation that pushes heat through windows and door frames, much less heat is lost to outside. This is particularly true in rooms with high ceilings and a lot of glass. And, air in a radiant heated room doesn't stratify at the ceiling like it does with forced air. Customers pay for the warmth right at their feet where they want it, not by collecting heat at ceiling level.

Hydronic, or water-based, radiant floor systems are used in larger areas or for an entire home. Generally, hot water radiant is best for spaces of 500 square feet or more, or in a building where hot water is already used as a heat source. Hydronic tubing can be embedded in concrete slabs or in thin slabs over frame floors, stapled up between floor joists, or installed on top of the subfloor.

"Hydronic radiant floor heating operates by circulating water at low temperatures, often in the 90 to 130 degree range," says Kolyn Marshall, a design engineer with Springfield, Mo.-based Watts Radiant. "Generally, the strived-for floor surface temperature for both hydronic and electric systems is a comfortable 70-80 degrees."

The Sum of Its Parts

Special distribution units, called manifolds, channel the heated liquid into multiple radiant floor pipe circuits. Manifolds are usually located close to the heated area, although they can be installed in a mechanical room. Each manifold set includes a supply (hot) and a return (cooler) manifold. Manifolds usually include balancing valves to control the flow of heated water to each circuit, or loop. Circuits are the loops of specialized PEX plastic or EPDM rubber tubing that begin at the supply manifold and end at the return manifold. The combination of manifolds and circuits heat a defined area that's called a zone. A zone can be one room or several.

One method, which entails the installation of plywood "sleepers" over existing floors or subfloors, is ideal for new construction or retrofits. This system provides the highest BTU output per square foot--important for rooms surrounded by windows where heat loss is greatest. The "SubRay" sleepers are screwed to the subfloor and tubing is laid between them (see photos). A floor installer then bridges over the system with any finished floor using hardwood, laminate wood products, tile or stone. This method adds only one-half inch to three-quarters inch to the finished floor height.

An electric system is often the best choice for spot heating in areas like a single master bathroom, a hallway, powder room or kitchen. Typically, low-profile electric floor radiant systems are installed right in the thinset used to set a finished tile or stone floor. Warm solid surface floors are popular for master baths, entries, kitchens and sunrooms.

In most instances, installers of electric radiant products first attach a cement backer board over the subfloor. The mats are then stapled or taped to the backerboard and thinset mortar is applied with a notched trowel just prior to setting tile or stone. An option, especially well-suited for remodeling projects where an existing solid-surface floor has no heat, is a new type of electric radiant mat by SunTouch that's approved by UL for joist bay applications. If you have access to the framed underside of the floor, these mats can be secured within the joist bays, just under the subfloor, and then insulated.

Electric mats are commonly installed with programmable controllers that use a remote sensor embedded in the floor to keep your feet at the temperature you select. A controller turns the radiant floor on when the room is occupied and off when it's vacant.

There's one thing to check on with electric products. Ask about electromagnetic field (EMF) radiation. EMF is generated by the flow of electrical current, and although the health impact is hotly debated, most experts advise you to minimize your expo sure. Some manufacturers offer very low, or zero-EMF electrical systems.

Warm the Whole House?

Radiant heating can warm an entire house so that supplemental heat is rarely required. If your customer's budget rules out heating the entire home with radiant, then they'll definitely want to know about the option of having warm floors in just those areas where comfort is most important:

* Masterbathrooms. Feet are bare and floors will be wet.

* Masterbathrooms. Feet are bare and floors will be wet.

* Great rooms or family rooms. Frequently, these rooms have open or vaulted designs where forced air heat would stratify. A radiant floor will warm every object in the room without drafts or noise, and without sending the heat up to the ceiling.

* Sunrooms. Such rooms maybe beautiful to look at, but can be terribly uncomfortable because conventional heating won't keep them warm.

* Kitchens and entrys. Bare feet will enjoy a warm massage all winter long. When visitors arrive, they can leave cold, wet shoes on the floor. And, when they leave, they'll have warm, dry feet on the way home.

John Vastyan is a journalist whose work focuses on the radiant heat, plumbing and mechanical industries. He owns Common Ground, a trade communications firm based in Manheim, Penn.



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