Radiant Floor Heat
I plan to replace radiators in the kitchen with the radiant floor heating system. The plumber said to do it on top of the floor (in cement slab). But I much prefer to install it under the floor. (I do not want to redo whole kitchen right now and I want to blow insulation under…
I plan to replace radiators in the kitchen with the radiant floor heating system. The plumber said to do it on top of the floor (in cement slab). But I much prefer to install it under the floor. (I do not want to redo whole kitchen right now and I want to blow insulation under the floor any way).
How much worst to have this thing installed under the floor? From physics point of view in both cases the heating is 100% efficient.
If this is a questions of increased time to get heat to the surface – I can just shift timing on the thermostat. Do I miss something else?
What about a situation where you have a concrete slab and then a tile floor? where is it considered best to put the radiant heating? For example, a bathroom or an addition that doesn’t have a true cellar.
Wood is a natural insulator. Masonry contains much less air and allows energy to pass through it much more effectively. That is why radiant heat installed above or below subfloors produces night and day results.
That should be “below to above” R-10 below to each R-1 above
Putting the tubing on top of the floor is more efficient.A slab is good but not required, you can use sleepers and heat transfer plates. Each method has advantages and disadvantages.
If you do put the tubing below the floor you need a 10 to 1 ratio in the R values, above to below. If you have 2″ of wood above[R-2] you need R-20 below the tubing to “drive” the heat where you want it. If you have many layers of wood above it will be hard to be efficient. Wood does not transfer heat well and is not very good for thermal mass.
Above or below heat transfer plates will allow for cooler water and increase efficiency. They are not needed if you use a slab.
There are systems designed to be installed under the subfloor, but I would suppose it is all a factor of how thick everything is. I have seen floors that had 5 or 6 layers of flooring on top of the subfloor. Do you know how thick your floor is?
Jock deBoer, AIA
deBoer Architects