Here's what John Straube, Ph.d, P.Eng., professor of building science in the Civil Engineering Department, School of Architecture, University of Waterloo, Waterloo, Ontario has to say about radiant barriers under concrete. (Scroll down to subhead: NASA's radiant barriers are useless when you pour concrete over them)

Hi Worthy,

Thanks for the link! That article is certainly clear that the product's R value is exaggerated. I have found other negative articles on the insul-tarp as well. I guess the product is too good to be true.

So if I go with the 2 inches rigid insulation on the basement floor, what should I do for the garage floor (garage is not to be heated)?

Carol

No insulation needed. If you don't want random cracking, have it cut within a few days after pouring--about a one inch deep cut front to back side to side with a masonry saw.

No insulation needed. If you don't want random cracking, have it cut within a few days after pouring--about a one inch deep cut front to back side to side with a masonry saw.

Thanks again Worthy for your help.

Carol