what is the R value

[air2spare]

of the fiberglass pipe wrap insulation with the white vinyl backing? this house is at least 40 yrs old.

[Midwest]

You can estimate fiberglass at about R-4 (3.5 - 4.25) per inch and be pretty close. There are different densities with differing R-values, but this should get you a rough figure. Go to Johns Mansville or other insulation sites and they may have more exact data for you.