Warming Up to Radiant Heating

Step barefoot on a floor warmed with radiant heat and you won’t want to step off. For consumers, buying into radiant heat is this simple, and for those who want radiant heat in their homes, nothing will come between them and the comfort and efficiency they want. For savvy builders and architects who want to separate themselves from the pack, offering this amenity will do the trick.

Builders, not architects, are always the early adopters of technology, as architects tend to have wait-and-see personalities,” says John Rose, president of Nuheat, which makes electric radiant systems. “That’s not a knock on architects. Architects are putting their reputation on the line, and want to make sure what they’re specifying is proven. Whereas builders want to be on the leading edge of technology to offer the latest lighting and heating systems, for example.”

From the architectural standpoint, radiant heat is the future of the heating industry, says Jim Lemen, national accounts manager, Vanguard Piping Systems, which makes radiant tubing and other system components. “Architects can set themselves apart and be innovative with their designs because with radiant there are no vents, so there’s no worrying about designing around any forced-air delivery systems,” he adds.

Architects and builders are slowly accepting radiant heat, based on a 37 percent increase in sales of tubing for hydronic (water-based) systems in 2004, the most recent year for which this information is available from the Radiant Panel Association. The RPA is an association of manufacturers, distributors, designers, dealers and installers of radiant panel heating and cooling systems and components. Sales of electric radiant heating systems increased 214 percent in 2004. Sales figures for both hydronic and electric systems are expected to increase again for 2005.

“I believe the advent of HGTV-type shows and the thirst of homeowners for information about radiant systems is probably a bigger driving force for radiant sales than a builder or architect having a liking for the product. In fact, I have seen a builder unsell a homeowner on his desire to put radiant in his home,” he adds.

Why would a builder unsell a client who wants a product that can increase a builder’s profit? Maybe because some builders might be intimidated by the radiant heat concept and need more education to be comfortable with it, says Jan Andersson, heating product manager, Uponor (formerly Wirsbo).

This is why it’s important to understand the technology. Radiant heating systems come in two main types: electric and hydronic (water-based). Electric systems consist of wires snaked on top of a subfloor but under flooring material. Hydronic systems consist of hot water piped either above or below a subfloor, but also below the finished flooring surface.

“One intimidating factor is the perceived interruption of other trades by having to install hydronic radiant. (Builders) believe the pouring of concrete, installing the proper flooring support, and a fear of puncturing the tubing will disrupt their schedules. This could happen, but it’s simply a matter of scheduling better with a little planning (to avoid this),” Andersson says

Custom home builders and architects are better positioned than production builders to include radiant systems in their homes. Their clients are more discriminating, says Dan Chiles, vice president, marketing, Watts Radiant, which makes both hydronic and electric systems. Some builders install hydronic tubing in the basement slab but don’t connect it. Then they market the home as “ready for radiant,” differentiating the builder and making happy customers, he says.

“Electric systems have done well because a builder can put electric radiant in a master bath and the kitchen, and it doesn’t cost much money. This becomes a selling feature and a way for the builder to differentiate himself and add value to his product,” Chiles says.

“Builders know which features provide the most bang for the buck. They make a list, including items such as stainless steel appliances, granite countertops, fireplaces, radiant heat, etc. Then they figure out where radiant falls in the minds of the consumer and what consumers will pay for it,” Rose says. “For example, it might cost $400 for a bathroom radiant installation, which is worth $2,000 or $2,500 when the home sells.”

System Design
Common resistance from builders and architects to choosing radiant is the process of designing a system. To help alleviate any concerns, manufacturers provide many services including heat-loss calculations, complete system design and layout including CAD drawings.

Still, even a project for which CAD drawings and heat calculations are prepared can be messed up if not installed correctly. If a builder hires the lowest bidder who pays no attention to the calculations and installs half a system because he was charging half the price, that’s bad, says Michael Willburn, technical assistance representative, Infloor Heating Systems. “Having the manufacturer-supplied plans is good in this situation in case that house does not perform correctly. You can go to the design and if it’s not a match with our CAD designs, then it’s the sub’s liability problem, not the builder’s.”

A big issue for architects to consider when designing a home with hydronic radiant heat is mechanical room size, Willburn says. “Too many architects and builders provide a 3-by-3 box to put all the (plumbing) equipment in. We require more room than for standard mechanical equipment, and need to vent it with a flue as well. Architects must plan for that.”

An argument against using a whole-house radiant system is also having to install ducts for air conditioning; so why not use forced-air heat? As an alternative to using radiant heat throughout an entire house, consider using conventional forced-air heating and accent it with radiant, Chiles says. “You’re decorating a house with little zones of comfort. It gets the builder away from having to decide on one system or the other. And if the zones are small and few enough, you can use a water heater to supply all those little (hydronic) zones. You can have a simple circulator, a couple of manifolds and some tubing.”

When choosing floor coverings for a hydronic radiant floor, water temperature becomes a factor. “Wall-to-wall carpeting has a higher R-value than wood or tile so some radiant systems require higher water temperatures to conduct the heat through (the carpet). With some systems with higher initial water temperatures to conduct the heat, you can top out and you can’t use carpet or other coverings because you can’t increase the water temperature enough to conduct heat through the flooring material,” says Ben Wyant, marketing director, Warmboard Radiant Subfloor, which makes structural subfloor in which radiant tubing can be snapped. Warmboard’s design allows for lower water temperatures, resulting in lower costs to heat the water, and a broader range of floor coverings that can be used in its applications, Wyant adds.

The reliability of any radiant system is assured with good design and installation, using proven products, says Lance MacNevin, manager, HP technical services, Rehau, which makes components and tubing for hydronic radiant heating systems, and plumbing and fire protection systems.

“Radiant systems are designed for each flooring application and floor covering so the pipes, fastening system, water temperature controls and installation techniques match the requirements of the building. In other words, the pipes are installed in the floor using methods that prevent damage during installation or due to building movement,” MacNevin says. “Manifold locations are chosen for access and to match the network of pipes. Modern controls will prevent overheating of the water and prevent damage to floor coverings.”

Cross-linked polyethylene (PEX) pipes have been used for more than 30 years for radiant heating applications. “These pipes are proven to be durable and reliable and are proven to last for many decades. Based on years of testing and field experience, the life expectancy of these pipes is more than 50 years. Manufacturers back their piping and fitting systems with long warranties,” he adds.

With careful planning by the radiant installer and good communication with the trades, accidental punctures of pipes during construction are rare, MacNevin says. “Still, if it happens, it will be revealed during the pressure test and can be repaired using reliable couplings designed for that application. Damage to pipes from external factors is easily prevented.”

Radiant Applications

In general, hydronic radiant is chosen for whole-house applications, and electric systems are used for individual room needs, typically as a secondary or complementary heat source, Rose says. “We never look at ourselves (Nuheat) as competing with hydronics. We are a secondary heat source. We’re not a heating product; we’re luxury comfort.”

Applying creativity to electric radiant systems can result in unique and interesting applications, such as warming the edge of a kitchen counter. “(We lay electric mats) 8 to 10 inches underneath the edge of a granite top and warm it up where people rest their elbows,” Rose says. “As soon as a builder sees how homeowners love this, they’re hooked. Also, claw tubs are becoming popular again. We have builders who put Nuheat mats under and around the tub, and even on the steps leading up to it, to warm the cavity the tub is sitting in. Because of radiant heat’s nature, the surface of the tub is warmed and the water doesn’t go cold in 10 minutes.”

Chiles adds, a client of Watts Radiant wanted to be outside on his deck and feel like he was on a beach, so a radiant system was installed under the deck, and the deck was covered with sand, which is warm to the bare foot thanks to radiant heat.

Such creative applications like these are no surprise to those in the radiant market, because the radiant world is one of emotion, whereas most of what people do with a house is governed by analytical, left-brain forces, Chiles says. “When people step onto a radiant floor, it’s an emotional experience. At trade shows, people say they’d rather give up their roof than their radiant floor. It’s not every day you can say that about a product in a house.”

The beauty of radiant heat is how it works, Uponor’s Andersson explains. Radiant heat warms objects and creates a smaller differential between air temperature and surface temperatures than forced air. One common myth about heat is that it rises, when in fact it’s hot air that rises, he adds. “Heat actually radiates in all directions. This is the reason radiant is such a good solution for great rooms with cathedral ceilings. With forced air you’re paying to heat all the air in the space all the way to the ceiling. But with radiant you’re delivering the heat only where the occupants are, close to the floor, and who cares what happens in the rest of the space above their heads? The heat stays near the floor where the people are.”

Conditioned air stratifies in rooms with tall ceilings and forced-air systems, Chiles explains. Cascading cold air forms near glass and fills a room. “Then you’ve got ceiling fans trying to blow air around and that makes a draft. It all adds up to discomfort. And the heating bills to keep the room warm become unbearable.”

For those who may have susceptibility to airborne health-related issues, radiant systems are great because they do not blow allergens around, says John Fantauzzi, technical director, Radiant Panel Association. “Plus, radiant is an even heat which eliminates temperature swings. Once you’ve experienced it, there’s nothing like it,” Fantauzzi says.

It’s not only comfort that hooks people on radiant heat, but it’s also efficiency and energy savings. In states with milder climates, radiant is sold on comfort. In colder climates, it’s sold more on efficiency, Fantauzzi says. “It used to be that utility costs drove people to one system or another, but utility costs today are closer in general so that’s not a factor as much anymore. The longer a heating season the more one can realize on utility savings.”

Education Matters
In situations with homeowners who haven’t been on the Internet to learn about radiant heat, the knowledge of builders and contractors is relied upon to help homeowners make educated decisions on radiant heat purchases. Unfortunately, this means the builder and contractor must be properly educated to give owners enough information to make an educated decision.

The RPA offers a four-hour educational course called Radiant Architecture. Attendees can qualify for 3.5 CEUs with the American Institute of Architects. The RPA has chapters nationwide that put on educational sessions for local builders and architects. Uponor also offers extensive radiant training in its state-of-the-art education facility in Minnesota.

Rehau developed an online course with Ron Blank Associates to educate architects on designing with radiant heating systems, MacNevin says. “The principles of radiant heat are explained, as are the capabilities and applications. The course explains how (hydronic) radiant systems using PEX pipes are integrated into residential buildings. Other applications of PEX pipes, such as plumbing, NFPA 13D fire protection and hydronic snow and ice melting systems are also introduced.”

The initial cost of radiant heat can limit its acceptance, but another restraint is its relative newness to many people who don’t know about it, Wyant says. “Some builders aren’t as likely to try radiant as others because they like to do things the way they have for years,” he adds. “One of our challenges is to get people to think of the better ways to do things like heat a home, and we have that better way.”

“As radiant becomes more mainstream, the price disparity between radiant and forced air will make it less prohibitive to put in radiant systems,” Lemen says. “And as radiant cooling technology from Europe becomes mainstream in the United States, radiant heating will become an integral part of residential design.”