I am trying to determine if it is better to use 2″ foam board or a combination of 1″ foam board and double bubble radiant barrier under my new concrete garage floor when using a hydronic radiant heat system. I live in PA.
This is a question you first need to run by your local building inspector to be sure you are meeting the codes. If you are going to use foam board, whether 1″ or 2″, I would not suggest you couple it with a reflective insulation. First a reflective insulation loses its ability to be a thermal block when its’ reflective surfaces are in contact with other surfaces. Second, it would be overkill in any case, depending on where you live, 1″ foam board would usually be sufficient. You only need to add a plastic film for moisture control.