HOMEOWNERS WARM TO radiant floor heating
An ancient approach to heating is gaining converts, but many homeowners don't realize the array of benefits offered by these efficient systems.
In a hydronic system, tubing is laid evenly beneath the flooring. This ensures no cold spots that can occur when heating with forced-air through vents or a radiating system such as radiators or a wood stove.
Master architects as diverse as the ancient Romans and Frank Lloyd Wright knew the benefits of heating rooms by placing the heat source beneath the flooring. But few modern homeowners have taken advantage of this approach. That's changing now as the array of benefits becomes better known.
"Homeowners are becoming more aware of environmentally friendly systems and the ways that they can save money while adding comfort.'  Design Engineers has been engineering radiant-floor-heating systems for over 25 years and has seen an upsurge in interest. "It's a lot more efficient than regular heat and it's more comfortable. "That's a strong combination."
The good old days
The technique has existed since ancient times, when Romans forced hot air under the floors in their villas. In the 1930s, noted architect Wright ran hot-water pipes through the floors of many of his buildings.
The reasons this approach has persisted over the years are multiple.
They include:
Comfort. "The number-one benefit is a more comfortable room. Because the heating source is wound underneath the entire floor, spaces heat evenly and from the bottom up, ensuring warm feet and bodies. This method heats the people in the room, not the air space, which is considerably harder to warm up.
Efficiency. "Even heat distribution may result in lower heating bills. The floor surface radiates approximately the same amount of heat as the human body, "making the occupant feel warm even though the air temperature might be only 65 degrees Fahrenheit." It also can radiate the heat for a long period without added fuel. "Radiant-heating fuel savings of 15 to 20 percent over forced-air systems are possible." But the report warns that savings start to disappear every time someone decides that 65 degrees doesn't seem like it could be warm enough and fiddles with the thermostat.
Complete control. Each room can be controlled separately, because floor heating is a low-temperature system that provides better zoning. The most effective systems incorporate outdoor sensors that adjust temperatures to exact weather conditions. "Placing a thermostat in each room will prevent overheating any space. This also allows systems to run constantly near windows, which will be cooler.
Design freedom. With the heating system under the floor, homeowners don't have to worry about keeping vents clear or placing furniture near baseboards or radiators. That provides more usable floor space in every room and eliminates the need to disguise or hide ducts or radiators.
Low maintenance. The systems have few moving parts, eliminating fans and belt that need replacing. As nothing disturbs the system, it can operate for decades. "The tubing for hydronic heating has been tested since the 1970s, and it's not going to leak, "The tubing is nearly indestructible."
Allergy reduction. With no circulating air, dust and pollen isn't disturbed, creating a healthier environment. This can be critical in new homes that are air tight, offering high-energy efficiency but reducing air exchanges that enhance indoor air quality.
Quiet. As a radiating system, radiant floor heating has no fans, ductwork or pinging pipes to make noise.
Basement options. Placing radiant heating beneath concrete, such as a basement slab, provides a strong radiating surface that can keep a room warm for a long time.
There are several types of radiant heating systems available. The three most common are radiant air floors, in which warm air circulates; electric radiant, which features heating coils; and hot water or hydronic radiant floors. Air systems are seldom used today, as they aren't very efficient.
The bulk of the remaining systems tend to be hydronic. "It accounts for about 90 percent of systems used today.
Hydronic heating is familiar to most people and has been used extensively in Europe for decades. There are plumbing companies in the U.S. familiar with the concepts and could learn the heating techniques quickly, spurring growth. They also are the most cost effective, typically using natural gas to heat the water. "Electric radiant floors are usually only cost effective if your electric utility company offers time-of-use rates. That allows the system to heat the flooring during off-peak hours, keeping it warm for eight to 10 hours before needing another warm up. Solar heated water is the most effective way used in radiant flooring to heat any structure.
Systems are installed one of two ways. In a "wet" installation, tubing is embedded in the concrete foundation slab, in a lightweight concrete slab on top of a subfloor, or over a previously poured slab. "Dry" floor installations have been gaining popularity, because they are faster and less expensive. One approach suspends the tubes beneath the sub-floor between the joists, which requires drilling through the joists and installing reflective insulation to reflect the heat upward. The tubing also can be installed between two layers of subfloor, typically in aluminum diffusers that spread the heat evenly. The tubing and diffusers are installed between furring strips, which carry the weight of the sub-floor and finished floor surface.
Ceramic tile rules
Because of its heat-absorptive qualities, ceramic tile is the most common floor covering used with radiant-floor heating. "Tile works wonderfully. But almost any flooring can be used, although some obviously will work better than others. Any material that provides insulation, like cork, will make the systems less efficient, and this impact should be taken into account.
Some contractors and homeowners have shied away from hardwood floors, fearing either nailing problems or shrinkage. But experienced contractors say it presents no problems. "The key with a new wood floor is to ensure that it's properly cured before installation. Typically, wood flooring comes out of the factory with a high moisture content, and problems arise when it is exposed to the direct heat. "Let it sit for four or five weeks to reduce the humidity level to 4 to 8 percent. We have many glue down and vinyl backed wood floorings available which are idea over lightweight concrete radiant floor systems.
Remodeling, too
Radiant floor heating doesn't need to be reserved for new homes or major renovation projects. Manufacturers make systems designed for remodeling uses, which can be tied into a solar collector or upgraded boiler. These work well for additions, such as family rooms or kitchens and bathrooms, especially when tile is used on the floors. For small bathrooms, you can use an electric mat, but otherwise, "I'd recommend a hydronic system for almost all remodeling situations."
There are several drawbacks to the systems, notably their price. They can cost considerably more to install than a traditional system, adding time to a project and more labor cost. It also can take a significant amount of time to heat up the thermal mass of a concrete slab if it cools off, producing a chilly room until the floor is radiating.
The initial cost can be a deterrent, but savvy homeowners look beyond that hit to the efficiencies, which create a quick payback and then keep paying back over the life of the system. And the comfort benefits create a compelling advantage, if Homeowners are aware of them. "They cost half as much to operate, which repays the cost quickly. "Customers like the return on investment the systems provide. But it can take time to explain the benefits and make homeowners understand the value of investing the money up front:'
The system's efficiency will improve as more solar water heating systems enter the market. "It's far more efficient. With the low temperatures that a hydronic system requires, I expect that to take off as solar panels become more prominent." Solar panels often can move from a back-up system to take over the heating load when only a little is needed. "Done right, it has a lot of potential.
Although radiant-floor heating can be used with virtually any type of floor covering, including hardwood, ceramic tile provides the ideal covering - producing a strong partner for bathroom remodels or additions.
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