So I'd like to install some pipe insulation on my heating and domestic hot water pipes to save energy, and I have some really dumb questions.
First, how big is a 3/4" pipe? I assumed the heating hot water pipe leaving the boiler was 3/4" and the return was 1/2", but then I tried measuring them. I measured the circumferences with a piece of string and then divided them by pi, and came up with about .9" and .6" respectively. Is the exterior diameter of 3/4" pipe actually some other size, like how a treated 2x4 piece of wood is actually smaller than 2" by 4"? What diameters are common in the U.S.? The insulation for 3/4" pipes seems to have an interior opening of about 1" -- is there extra room for irregularities?
I heard from a plumber that black foam pipe insulation is useless and doesn't even have an R value, and that I should get the paper-wrapped fiberglass insulation instead. Is this true?
What precautions do I need to take when dealing with fiberglass? Are rubber gloves enough? What's the best way to cut it?
Thanks, Apr