Combine subfloor and radiant heating and you get: Radiant heating subfloor, of course! Sure, it's a novel idea. But it's the logical conclusion when you think about subflooring, underlayment, and radiant heating–currently, separate processes.
If radiant heating is installed farther down the road, then yes, they must be separate processes. But if you know from the start that you'll be installing radiant heating, why not just nail down radiant heating subfloor?
It does make perfect sense. But because nothing in this world is perfect, there are a few caveats which I will get to later on.
What Is Radiant Heating Subfloor?
Every floor covering or finish floor--that is, hardwood, engineered wood, laminate, etc.--needs a subfloor. Subfloor provides a solid and smooth base for the finish floor. If the subfloor isn't of sufficient quality to lay the floor covering, an underlayment may be needed. Subfloor tends to be plywood--5/8" or greater CDX plywood graded A/C is one type of subfloor you may find.
Hydronic radiant heating subfloor takes the basic idea of plywood subfloor and goes a bit further:
- 1 1/8" plywood. The thicker plywood is needed to accommodate channels.
- Channels or grooves cut into the plywood.
- Aluminum skin conforms to the top of plywood and channels.
- Flexible PEX tubing snaps into the channels--heated water runs through the PEX and provides the heat.
Is Radiant Subfloor Better?
Putting aside the issue of cost, radiant subfloor panels tend to be an excellent option. The energy from radiant heat tubing embedded in concrete is quickly dissipated, whereas the energy from radiant panels is reflected room-ward by the aluminum sheathing.
Also, because of the channels, the radiant heat tubing is allowed to rest higher and with fewer impediments than other methods. These channels--pre-cut in the factory--also ensure that the tubing is spread out across the floor in a balanced manner.
Installing Radiant Heat Subfloor
While it's not rocket science, radiant heating subfloor involves a bit more than just buying the panels and handing them over to any old crew for installation. The panels are costly, so you want to minimize waste as much as possible (though waste materials are inevitable in any remodeling or building project). The layout of the panels involves actual planning ahead of time, rather than just doing it on the spot. Finally, once the subfloor panels are in place, there is still the matter of running the tubing and installing the manifolds.
- Plan out your subfloor panel layout.
- Separate different types of radiant heating panels (right, left, etc.).
- Screw down panels, as you would any other type of subfloor.
- Cut out grooves for special exceptions, such as around a toilet.
- Snap in the PEX tubing and press it flat with a roller.
- Connect to manifolds.
- Pressurize system to check for any leaks.
- If not ready for the floor covering yet, protect it with thin plywood.
- Install finish floor.
Looping the radiant heat tubing through plywood channels is far superior to embedding it in wet concrete. Keep in mind, though, that when nailing down hardwood or engineered wood flooring, the installer needs to zealously avoid hitting the tubing with the flooring nails/staples.
For the observant installer, this should not be a problem--the brightly-colored tubing is clearly visible in advance of the line of flooring installation. But I can also see where this might be a problem for any installer who has never worked with radiant heat subfloor (which describes the majority of installers) or installers who simply don't care enough to keep an eagle eye on things.
Because of this, I recommend working only with known or highly recommended flooring installers to install the floor covering over your radiant subfloor.
Is Radiant Subfloor Heating DIY-Friendly?
Little about the installation of these systems goes beyond common knowledge that an intermediate DIY-remodeler knows. There is a bit of specialized knowledge, but it is clearly explained--that is if you go the Warmboard route (explained below).
All that said and done, it still does not appear to be streamlined for the do-it-yourself remodeler. Warmboard heating needs to be planned with the help of the architect and/or contractor in charge of the project. And you won't find Warmboard anywhere on the shelves of Home Depot: it must be ordered from the company itself.
So, it can be installed by a determined DIY'er. Otherwise, I say leave it to the pros.
Sources For Radiant Subfloor Heating Panels
Warmboard is the most visible face for heated subfloor panels. Be sure to check out their website (link below), as their videos give a good overview of what is involved with installation.
A trade group called the Radiant Panel Association covers all types of radiant heating systems, including radiant subfloor. For homeowners, the main value of the RPA site is its Member Directory, where you can find heated subfloor manufacturers and installers.