Ok to use larger diameter fiberglass insulation than pipe?

bipbap

I am going to insulate the steam mains in our basement. I already have a whole bunch of fiberglass pipe insulation for 3 inch pipes but our pipes are mostly 2 inch in diameter. Does it make any worthwhile difference to put a slightly larger size insulation on the pipe? I guess it just means there's a 1" or so of empty space between the pipe and the insulation and I'm just not sure if that is worth going out and buying all new insulation at the exact right size for the pipes.
Any thoughts?

Kahooli

as long as there is no air gap on either end to create a convective channel it should be okay.

EBEBRATT-Ed

Bite the bullet and buy the correct size. The oversized will not work very well

New England SteamWorks

With a little math and practice, you can determine the exact amount of the 3" that needs to be removed to make it 2". Once determined, make a long lateral cut into the insulation with a razor, remove, -and apply. This technique works fine going down one size. Won't be pretty going 3" to 2", but will work. For anything smaller, -buy the correct size. And if you are doing it yourself, -spend the extra and get 1-1/2" insulation.

I would not put 3" insulation on 2" pipe.