Concrete Slab Insulation – Reflective Barrier
I have a house (1976) with a concrete slab, that to my knowledge, is uninsulated or very poorly insulated. As you can imagine it makes heating costs very high. The 1st floor is about 1000sqft of which 150sqft is tile, and the rest is carpet over a thick carpet pad. I am tearing up the carpet this summer and installing hardwood floors over the slab. I am planning on a poly or paint on vapor barrier and then 1×4 PT bunks secured to the slab and spaced either 12″ or 16″ OC. Need to do some testing on what will be the best spacing to prevent flexing and bowing of boards. While everything is torn apart I would like to add some sort of reflective barrier or insulation to the slab. Adding several inches of foam or similar is not possible because the ceiling is already under 8FT and I am tall and don’t want to lose any more ceiling height and have to raise a bunch of door frames.
So that quickly ruled out foam board or any sort of faced batt insulation. In my search for reflective barriers I came across this:
Is this actually R-21 as the website says? I’m a mechanical engineer so I understand how heat transfer and R values work and I find it difficult to believe that the radiant heat transfer coefficient is small enough to produce a R value of 21. In my experience radiation heat transfer typically isn’t expressed in R values and the contribution of radiation to overall heat transfer (Q) is typically very small. But after some digging I did find an equation expressing R values of radiation with respect to a “radiation heat transfer coefficient” which I understand to be a film coefficient based on the equation Q = emissivity * (SB constant) * area * (T^4-T^4).
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