It has always been my personal conviction that radiant walls are among the most overlooked potential applications of radiant for residential space heating. It makes the most sense if you look at it from my perspective.
In both retrofit and new construction, construction details for radiant floors almost always have some additional cost associated with the installation of the heating system. It may be the extra sole plate or beefier floor joist or other structural requirements. Those costs aren’t always added to the installed cost of the floor heating system, but they should be, because without the floor heating system these other modifications would not have been necessary.
In the case of a radiant wall, the added costs are minimal. In most situations, other than the actual heating system, the only additional cost is for the insulation, assuming that an internal wall is used.
In retrofit floor cases, where the builder decides to raise the floor finish height, the loss of 112 in. to 2 in. of floor-to-ceiling height doesn’t seem like it would make a lot of difference, but it does. It is definitely noticeable. In addition to this minor hindrance, the builder needs to cut off all the doors by the additional floor height.
When coming into the home, this 112 in. to 2 in. of additional floor height can be a trip hazard. Building inspectors have shot me down over this issue before. You also must either raise all the counter tops by 112 in. or pay a substantial monthly fee to your massage therapist to work the kinks out of your neck from hunching over. Raising the counter tops affects wall finish in the area where the counter top was raised.
None of this is meant as a deterrent to anyone who “by golly, wants radiant floors” and is willing to pay the toll to have this type of comfort system.
In fact, I demand radiant floors in bathrooms, where it works and fits. Let’s face it, we spend a lot of time in this particular room with little to no clothing on, and we’re usually wet. Might as well be as comfortable as you can be, given the circumstances.
But I digress. Back to the advantages of radiant walls.
As it pertains to our physiology, radiant walls make more sense. Think of radiant energy shining like a large flashlight, and wherever and whatever shape of the shadow your body casts represents the amount of energy directly absorbed by your body. The bigger the shadow, the more energy is absorbed.
If the light is shining from above or below, the shadow cast is relatively small. If the light is shining from the side, the shadow cast can be substantially larger. Hence, your body should feel the difference in the form of higher thermal comfort.
In the case of a retrofit wall, the intrusion can be as little as no impingement on room area to as high as a 2-in. loss of internal floor space for the length of the radiant wall. Hardly significant.
If it’s an indoor wall, there may not be a lot of modifications necessary to include the overlay installation. Electrical box extensions are commonly available to handle the change on finish thickness.
If the radiant panel is to be installed in a wall with a door or window, jam extensions may be required, but that’s hardly a major detail, in my opinion.
When you select the radiant wall, you should think thoughts such as, “If I were living here, would I park my 7-ft. armoire or china cabinet against this wall? Would I ever want to hang a 6-ft. picture requiring mega wall anchors in this area?”
While it is impossible to think of everything that future occupants might do, it can come in handy to think about your alternatives. And by all means, bear in mind that it may become necessary to repair the wall if someone violates your tubing.
The nail-in-the-wall issue can be overcome if the homeowner agrees to use nail-free picture-hanging alternatives like those made by companies like 3M. In the case of the Habitat for Humanity home (October, pg. 34), the new homeowner has agreed to not put any pictures in the walls containing the radiant panels. This works well for him, and we can only hope that he remembers to convey this requirement to any future occupants of the home. Just to be safe, we installed a permanent record and plaque showing the locations of the radiant walls, along with a permanent set of photographs showing the exact locations of the walls and their tubing.
I still expect someone sometime will “find” one of the tubes for me in the future. Just like they do with radiant floors.
One means of avoiding fasteners is to install the radiant panel only in the lower 4-ft. wainscoting section of the wall. While this doesn’t guarantee a puncture proof installation, it helps to avoid potential damage. Then there’s always that poor unsuspecting cable guy just waiting to make your acquaintance.
Tune in next month as we continue to delve into this uncharted area of hydronic radiant heating. Until then, Happy Educated Hydronicing!
Mark Eatherton is a Denver-based hydronics contractor. He can be reached via e-mail at [email protected] or by phone at 303/778-7772.