Retrofitting Radiant Heat
In USA, radiant heating only commands about 6 percent of the home heating market, but homeowners who have it rave about its comfort and efficiency, despite the fact that the up-front costs are usually higher than other systems. These homeowners are taking a long-range view, says Dave Yates, president of F.W. Behler plumbing and heating contractors in York, Pa.
“Most homeowners invest in high-efficiency equipment, such as boilers with 92 to 99 percent thermal efficiency,” he says “They see it as a wise investment in comfort that pays for itself in a few short years.” Owners also love the fact that radiant heat is quiet, heats evenly and eliminates the problem of dust and other irritants associated with forced-air heating.
So radiant heating may be a clear choice for new construction, but what about remodeling? Many contractors still think that radiant heat is too difficult to retrofit into an existing home with some other type of heating system. Dave disagrees.
“We haven’t met a house we couldn’t retrofit,” says Dave. “It’s actually a fun way to go, because you’re dealing with the homeowners directly. You get to be an educator as well as an installer.”
Dave adds that new technologies and products can make any home a good candidate for radiant heat. Among the most common methods for radiant heat retrofits are the following:
* Thin Slab. The heating elements are attached directly to the wood subfloor and a concrete, lightweight-concrete, dry pack or gypsum underlayment is installed as the final subfloor. (Concrete needs a slip sheet under it to prevent bonding with the wood.) A fairly low source temperature is all that is required with this method.
* Subfloor plates/subfloor board. Aluminum plates with channels for the tubing are installed over the subfloor, supported by boards attached directly to subfloor).The plates spread the heat uniformly, and these methods allows for hardwood floors to be installed over them.
* Engineered subfloor. The structural subfloor is replaced by engineered, load-bearing boards topped by a laminated layer of aluminum with tubing channels. As with the previous method, hardwood can be attached directly to the plates.
* Staple-up. Tubing is attached to the underside of the existing subfloor in the joist spaces, usually with a two-inch airspace between the bottom of the subfloor and the foil-faced insulation that must be installed beneath the tubing. If aluminum plates are used to cover the underside of the subfloor, the insulation may be pushed up tight against the plates.
* Hanging in joist space. Tubing is suspended several inches beneath the subfloor in the joist space. Insulation is then installed with a two- to four-inch airspace. The tubes heat that airspace, which then heats the subfloor.
All these methods require different source temperatures. It is sometimes possible to scavenge the heat from an existing hot water heater. Dave cautions that there are some bacterial issues with using this method (legionella bacteria from the heating system can sometimes get into the potable water supply), but these are typically remedied by installing a simple flat-plate heat exchanger. (More technical information on source temperature requirements, heat loss calculations and other installation conditions are available at www.radiantpanelassociation.org.)
Dave says the most important thing to remember—no matter which method you choose—is to make sure that what you install is going to perform up to the customer’s expectations. “The physical construction will greatly determine which method is used, but so is the heat-loss calculation. All the tubing manufacturers have great programs to help contractors figure heat loss.”
Another radiant heating method that is gaining in popularity is the use of electric mats. Electric elements are embedded in some type of thin-set material on floors, or manufactured panels can be installed on walls or in ceilings. Some operate on low voltage, some on line voltage, but all require high limit sensors, ground fault protection and thermostats in the room being heated.
“These are great for spot heating, such as a bathroom, kitchen or entryway,” says Dave. “But they can be impractical in areas where electric rates are a little high.”
Source:hgtvpro.com