My folks lived in a 100-year-old house, complete with cast iron radiators. They were big, heavy, and wheezed a lot (the radiators, that is), but what a great place for us kids to put wet mittens after a day of sledding. Plus, they gave off radiant heat, the most efficient, direct form of heat because it warms objects and does not use air to transfer heat. While cast iron radiators are rarely installed today, their benefits can be had in panel radiators, which are made from cold rolled steel and often sport a powder paint finish. Panel radiators lend themselves well to remodeling projects, particularly those where their high BTU-output and compact size is a benefit over traditional baseboard radiators that spread themselves around a room's perimeter.

Charlie Bethel, a Burlington, Vt., plumber passes along these tips for adding panel radiation to an existing hot water heating system: Size the radiator to the calculated heat loss for the space; check the BTU output of the boiler to be certain that the new heated space won't exceed the boiler's capacity; and install a monoflow valve on the return side of the heat loop, which will direct return-side hot water back to the boiler.

But the secret to panel radiators is PEX-AL-PEX, a tubing sandwich with inner and outer plastic casings surrounding a thin-wall aluminum hose. When the tubing is bent, it retains its shape, thereby minimizing the number of retainer clips that secure the tubing in place. It has the same coefficient of expansion as copper, which translates into reduced expansion and contraction of the conduit, a common problem with other tubing, such as rubber or PEX. Available in 250-foot coils, an installer can make a "home run" connection that goes directly from the boiler to the panel radiator.

Compression or crimp-on fittings allow for connections between the tubing and copper pipe or radiator. The compression fittings are tightened with adjustable wrenches; the crimp-on fittings require specialty tools.

With PEX-AL-PEX tubing, an installer can snake through obstacle-ridden areas where rigid tubing might require additional demolition or contortions. For example, in a second-floor panel radiator installation, tubing could be run parallel to floor joists without removing the ceiling below. At the tubing ends, fittings attach to the radiator and to supply and return heat lines. Rigid copper requires soldered fittings and therefore accessibility to solder those fittings.

But this convenience comes with a cost, at least for materials. To get the equivalent BTU output, panel radiation will cost about four times as much as fin baseboard radiation. The PEX-AL-PEX tubing is equivalent in cost to copper; the fittings are more expensive, but fewer of them are needed. The labor savings, however, can be substantial, because a less skilled person can run the flexible tubing. Costs are also reduced because there's no need to create access points for rigid copper.

And there's always the side benefit of offering a place for your customers to put their wet mittens.

--Lee McGinley, CR, a Big50 remodeler, has written for The Journal of Light Construction . He lives in Addison, Vt.