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.

negligible by themselves...

I did not know it has any R-value

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'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.