Radiant heat in a ceiling
I’m finishing my basement and was wondering about installing radiant heat in the ceiling. Can I let copper tubing rest on top of the drywall for heat transfer, or does the tubing need to be embedded in a plaster ceiling? Are manufactured ceiling panels available, and should the basement be on a separate heating zone?
Bob Prosser, Sarasota, FL
Jonathan R. Smith, owner of Effective Air in Glenview, Illinois, replies: A radiant ceiling is an excellent way to heat your finished basement room, but I wouldn’t recommend copper tubing for any radiant system. Also, attaching radiant tubing to drywall is not a good way to create a radiant panel. However, there are several other ways to build the radiant system you’ll require.
The problem with using copper tubing is that it corrodes, especially where fittings such as elbows and couplings are inserted. Regular plastic tubing, on the other hand, can become brittle and allow oxygen to enter the system, which in turn accelerates the deterioration of your heat source, i. e. your boiler. A better alternative is using cross-linked polyethylene tubing (called PEX tubing), which is designed specifically to resist corrosion and to prevent oxygen diffusion. One manufacturer, Wirsbo, now known as Uponor (5925 148th St. W., Apple Valley, Minn. 55124; 800-321-4739), also makes aluminum heat-transfer plates that snap around PEX tubing to create radiant panels that can be mounted between ceiling joists. These transfer plates help to maximize heat distribution and radiation from the PEX tubing.
Another way to heat your basement from above is to install radiant-panel radiators on the finished ceiling. These heaters are made by a number of different companies and are available through most companies that sell HVAC supplies.
Regardless of the system you use, I recommend putting the basement on a separate zone because of its different heating requirements. If you use a system such as the Wirsbo PEX system, you’ll need to maintain a design temperature for the water at 10°F, which requires a mixing valve and manifold system. I don’t recommend using the hot-water return off your existing baseboard-heating system because it would be difficult to control the amount of heat in the basement with any accuracy.
By the way, electric radiant-heat ceiling panels that would eliminate the need for additional plumbing are also available. For more information, contact the Radiant Panel Association at (612) 682-4844.