How much insulation should be installed in conjunction with radiant floor heating?
Some applications of radiant floor heating require more insulation than others and some may not require any. If the radiant floor system that you are installing or having installed is part of the building envelope, like a basement concrete floor or garage concrete floor, then it is imperative that the proper amount of insulation is installed so that the radiant floor system can function efficiently.
In the southwestern region of Ontario, Canada, the Ontario Building Code (OBC) requires R10 insulation to be installed with radiant floor heat systems. The rate at which heat moves out of a building depends on a couple of variables. The first variable is the delta between the inside and outside temperature, and the second variable is how well the rest of the structure is insulated. Many professionals agree that the more insulation you have in the building, including walls and ceilings, the more you should put in the ground. After all, the ground is a part of the building envelope.
Many people will install more than the standard R10 in an effort to isolate the ground from the radiant heat source, forcing more heat upwards. Remember, hot air may rise, but heat moves from hot to cold; therefore, the more you insulate the rest of your home or commercial building, the more heat you force to the lesser insulated areas, which typically include windows and concrete slabs. The more insulation you put under the floor slab, the less heat goes into the ground.
If radiant heating is installed on a floor system that has leaving space below it, the insulation is not as critical, but it still is a good idea to isolate it as best as possible so you can maintain effective zoning. Insulating these radiant floor areas may also help with sound and acoustics.