Contractormag 1780 Eatherton

Exploring alternative radiant heating surfaces — Pt. 4

Aug. 30, 2013
As I pointed out in my last article, there are many different ways to deliver radiant comfort without having to utilize the floors.

As I pointed out in my last article, there are many different ways to deliver radiant comfort without having to utilize the floors. In the three previous articles, we covered my personal application of a radiant wall system. When I did that system 12 years ago, radiant walls were not being utilized in the mainstream applications. Sine that installation, I have seen and been exposed to many different methods of application, all with their pluses and minuses. In the next few articles, I will attempt to explain them in more detail to make your job as a comfort delivery technician much easier and help you avoid having to be the pioneer in the field like I was. I will start with the system that I am most familiar with, which I documented in the previous articles.

My methodology started out with the intention of using those light aluminum flashings that have a groove rolled/bent into them to allow them to receive the tubing. Their original intended application was for radiant floors. They were to be installed below the subfloor to allow a better heat transfer than can be expected from a staple up or suspended tube application. Regardless of whether it is radiant walls, floors, ceilings or countertops, always remember that conductivity is the king of heat transfer. It requires a lower water temperature than any of the other methods, with the possible exception of being embedded in a cementitious material. While it is possible to apply a cementitious material to a wall, doing so is very material and labor intensive, and one of the goals of the new RPA is to lower your installed cost of delivering radiant comfort, not increase it.

My original conception, which would still work perfectly in a retrofit application, was to install 1-in. x 2-in. strapping in such a manner that the strapping or furring strips would support the aluminum flashings and keep them in intimate contact with the final sheetrock covering. Again, bear in mind that conductivity is the king of heat transfer all the way through the system’s construction assembly. We even went to the extent of overstuffing the fiberglass insulation into the walls prior to applying the heat transfer sheets just to give a little bit more pressure and spring to keep the plates in good contact with the sheetrock. The plan worked on paper, but was a little more labor intensive than what I really wanted, and a lot slower than I had anticipated. I opted instead to develop a template that allowed me to use a ¾-horsepower outer with a 1-in. round nose bit that would allow the plates to be installed flush to the outer face of the stud. The “template” was made out of ½-in. copper tubing, and it had extruded aluminum heat transfer plates snapped onto the copper to give me the required guide/spacer to achieve the necessary 12-in. tubing centers.

That summer, I had an apprentice who was basically mechanically inclined, but had never done any carpentry/woodworking. I used him as a training experiment, and it worked out quite well. He caught on very quickly, and we knocked out the grooving for all of our radiant walls in one day. I still have the template that we used to develop that system hanging from the roof of my carport. I intend to recycle the components some day and turn them into a radiant wall panel heater or something of benefit. Another distinct advantage of directly burying the tubes into the face of the wall was that we avoided the additional floor space that would have been consumed by the wood strapping. It also didn’t cause any problems for the electricians. If we had we gone forward with our original intent of furring out the walls, the electricians would have had to do additional work to compensate for our installation. Always bear your fellow tradesman’s best interests in mind – it will come back to pay you in spades. Lastly, when setting up the tubing centers, it is wise to keep the heat-emitting tubing as far away from the electrical outlet boxes as possible to avoid overheating the electrical box and wiring components. It will also make the electrician’s job of installing the electrical outlet boxes much easier.

Tune in next month as we continue looking at alternative radiant heating surfaces in our efforts to “Grow Radiant.” If you have not yet become a member of the new RPA, by all means go to our website at and get signed up. It is an inexpensive way to support your industry, which is here to support you.

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