R-value of single ply?

Without insulation, TPO, PVC, EPDM has, what, about .5 R-value would you say? Doing some marketing, want to be accurate.

I'd be shocked if it was that high. I've never bothered to try and assign an R to any water proofing. Thermal mass of a thick BUR with gravel is probably the only only surfacing that would have any useful energy efficiency and even that's negligible.

Unless there is sun radiation, both sides of a single ply will be the same temp. Conductive heat transfer or something. (I'm just trying to take the discussion up to the 8th grade level to annoy Tim.)

I did not know it has any R-value

negligible by themselves...