LittleBittyBigJohn
Veteran Member
The water heats the pex tubing -> the pex tubing conducts heat to both the sub-floor and aluminum plates -> the warmed aluminum plates and the plywood sub-floor radiate infrared light downward away from their surfaces -> the foil bubble wrap reflects that infrared light back up towards the sub-floor and plates adding additional energy. The infrared light will bounce back and forth between the plates and the foil, but some of that energy gets absorbed by the plywood subfloor, some of it diassapates into other parts of the structure like the open web trusses and is lost via conduction out to the OSB sheathing and then the steel siding which is exposed to the outer elements.
The foil bubble insulation R value is pitiful, only like R2, but, the foil radiating the infrared light back up is the important part.
Underneath the foil bubble wrap will be fiberglass insulation to keep heat in the shop & garage produced by the pex in the concrete floors. Some of that heat will of course migrate up and heat the rooms above.
I would not be using this type of heat if I didn't have pex imbeded into the concrete in the shop/workshop below the second level living space.
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This is the same stuff I have in my metal shop building. It does a really good job keeping the heat out in the summer time. I could see how this would be good for reflecting the heat back up to the floor. But you are correct about the R-Value. It's not really any insulation at all.