Hydronic heating takes a whole-system approach

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Hydronic, or water-based, systems have become one of the most popular and often the most cost-effective whole-house radiant heating systems for heating-dominated zones.

According to the Department of Energy, hydronic systems average 26 percent less air leakage and a 40 percent reduction in energy usage versus forced air heating systems. Because the system heats from the ground-up, lower temperatures are found at ceiling height, resulting in lower heat loss through ceilings or ceiling penetrations.

Jason McKinnon, product trainer at Viega, says there are a variety of retrofit installation options for contractors to offer. These include panel, slab, thin-slab, snap-panel and heat transfer plates, all of which can deliver hot water via PEX tubing in either "wet-mass" (i.e. concrete) systems or non-concrete "dry-mass" installations.

"We're not out to say one is better than the other. It's not one method versus another. In most cases we're just looking to make installations faster and smarter. If that means we package the valve and a pump together to go with the PEX, then that's what we'll do," says McKinnon.

Thick concrete slab systems, which the DOE says are the most common, have a high heat capacity and are ideal for storing heat from solar energy systems, which have a fluctuating heat output. The downside of the thick slabs is the slow thermal response time. The DOE says most experts recommend maintaining a constant temperature in homes with these heating systems. "If I heat concrete all night long and shut it off during the day, it'll radiate heat all throughout the day. People don't realize that. (They) expect the heat to react quickly like a forced air system," says McKinnon.

Other installations, such as snap panels, are a dry-mass approach. Snap panels are aluminum panels heated by 3/8- or ½-inch tubing. Most measure five to six inches wide and less than two feet in length. These offer a lower up-front material cost than some wet mass systems and allow contractors to profit a bit more on the labor side. "Every manufacturer has them," says McKinnon. "Again, each installation is different. Are you coming up through an unfinished basement? Are you going to have to tear the floor out anyway? If you're doing any sort of slab work, my advice is to put a wet mass system in and be done with it."

The Other Side

While hydronic systems are mostly made for a whole-home approach, electric radiant heating methods can be an equally viable alternative in the right application. Electric radiant floors, also known as dry installations, typically consist of electric cables or mats built into the floor. Systems that feature mats of electrically conductive plastic are also available and are mounted onto the subfloor below a floor covering such as tile. These are pre-built like an electric blanket and are divided into sections, then wired to a central location. Many systems consume a mere 10–20 watts per square foot at full power consumption and can be set to pulse on and off to maintain the temperature the homeowner sets. Given the relatively high cost of electricity in the winter, the most common application for ERH is kitchens and master bathrooms.

John Rose, president of electronic radiant flooring manufacturer NuHeat, says, remodels are the most common application, and the Midwest, including Minneapolis and Chicago, keep the most business.

Cost/Benefit

No matter what option, hydronic radiant floor systems pump heated water from a boiler through PEX tubing laid in a pattern, whichever method chosen, underneath the floor or in the walls. The cost of installing a hydronic radiant floor includes the boiler, which will take the place of your gas-fired furnace. Though every installation is different, new residential boilers average around $5,000, with whole-house systems often running from $20,000 to $25,000.