Not only does it provide high r values but foam board insulation is also easy to install lightweight and can be used in any room of your home.
Rigid foam insulation under subfloor.
But insulating your floors is a good idea for many reasons including energy efficiency and height adjustments.
The top layer of subfloor steps back and gets a layer of peel and stick flashing tape to form pan flashing under the sliding doors.
The foam butts against the mudsills for a complete thermal break.
There are two ways to handle insulating concrete floors.
Insulate the band joist with batt insulation as well as the crawlspace access if it s located in the wall.
You want it snug but not to.
Concrete basement floor.
You can attach wood sleepers to the floor fill the gaps with rigid foam insulation and then apply your finish flooring.
6 install rigid foam board or batt insulation exterior foam interior foam or interior batt to achieve complete insulation coverage.
2x4 sleepers installed on center every 12 16 inches and fastened down with rigid foam insulation 1 1 2 inch thick placed between the sleepers.
In other words rigid foam can be applied on walls foundations and roofs and works great for both retrofits and new constructions.
Or as demonstrated here you can cover the slab with rigid foam insulation add two layers of plywood and then add the finish flooring.