If you are a homeowner in Brooklyn or NY and get it into your mind that you want to install radiant flooring yor first step will be to do some research on the web. Several hours later you will most likely leave your computer in a confused daze of information overload and conflicting blog posts.
Here is my input which hopefully will reduce confusion.
Concrete vs. Wood
Concrete radiant flooring has the tubes in the concrete. There is no separation between the tubes, the concrete and the tiles. This is going to pull the heat out very well. The heat is quite even over the floor and requires a low hot water level, thus needing less energy to heat it.
Historically concrete creates a better radiant floor experience over wood.
But your heating should not dictate what kind of flooring you have in your house. Lets say you want wood.
Warm Board
More recently people have developed good ways to use wood flooring with radiant heat and it comes very close to concrete. The most well known brand is WarmBoard but you can easilly make it yourself if you are a DYI kind of green contractor. We have a post on how to make this on this blog.
The basic concept is a sheet of plywood with grooves cut out of it. If you buy it off the shelf the plywood acts as the sub floor. If you make it yourself you put one layer of plywood and then another layer in 8″ stips with an inch space between them to make the grooves.
Over the top is a layer of aluminum that also bend into the grooves. The pex tubes fit snugly into the grooves. If you are doing it yourself I recommend pushing a mix of concrete around the pex and aluminum groove to eliminate any air pockets. This really creates a great combination of mass and conductive material. Then the wood floor goes over that. Because aluminum conducts heat better than concrete this warm board gives a very good result. Most would agree that this is comparable to concrete. I have not seen tests on which is better but I would like to.
If for some reason you can’t get under the floor your other choice is to put the pex under the existing subfloor between the joists. This is not optimal because the heat has to pass through the subfloor. You have to run the water at hotter temperatures to get the same result so it is more expensive.
Most people put aluminum fins around the pex to help pull the heat out and distribute it. That works well. We have wrapped the pex with concrete that was put int black piping insulation that was cut in half. The insulation is on the bottom and the concrete is pushed up to the sub floor. THis gives a great heat sink to pull the heat out of the tubes and is insulated from below. We also blogged this method. We prefer it since it is cheaper than aluminum and has less embodied energy.
So…how much difference does it make what flooring you put on top? Concrete or a well crafted combo of subfloor with aluminium and wood are pretty close in effect. You can keep your water low and still get a nice cozy floor. Under the joists is not as good. You do need to spend more on heating the water. But it is done a lot.
The trick like all of this energy stuff is to focus on sealing up the house and insulating it really well.