Fiberglass vs foam insulation for basement steam pipes?

Tony Conner_2

... it's specifically made for hot (as in STEAM HOT) service - like Foamglas (expensive if you don't need it to be waterproof, stinks when you cut it, and generally nasty to work with as it's very abrasive) - ordinary foam will just melt. Fibreglass is the norm. They supply tape for the gaps where the ends of the sections butt together. Using it keeps air from circulating though these little gaps, which adds up on the heat loss.

Sarah Johnson

We had asbestos insulation removed from our pipes and now the basement is too hot and the third floor radiators don't run consistently. We want to re-wrap the pipes but aren't sure which is better, fiberglass or foam. Any suggestions?

We also want to clean the vents, some make hissing noises, but aren't sure how to get them off without breaking them. Any tips?

Thanks in advance from a new homeowner and radiator user!

Pete_18

Insulation

We used 1 inch fiberglass insulation on our mains and 1/2 inch fiberglass insulation on the risers where we could reach them. The 1 inch we needed to buy from the local plumbing supply house, the 1/2 inch was cheaper at Home Depot.

As far as hissing radiators, you may want to make sure that you have main vents and that they are the proper size. Generally speaking, if they're not Gorton's, they're not good enough. If you post the width of your mains and lengths, someone can let you know how many Gorton 1s/2s you need on your mains. Once you do that, you'll want to then worry about your radiator vents which would probably be better off if they were replaced with properly sized Gorton vents (only available at good plumbing supply stores or online).

Brad White_9

Fiberglass

Absolutely. (Foam glass really does stink when you cut it and embarrasses in mixed company .

Seriously and to take minor issue with another posting in this thread, the thicknesses required by model energy codes are greater than what was shown.

Here in Massachusetts we have a pretty good energy code (Ch.13, 780 CMR) which is consistent with national model codes used by many states. You may not be "required" to use these in a short retrofit application (no one will police you), but the intent is sound and you should at least know what the code says for reference if nothing else:

The applicable category is for 201 to 250 degrees which of course covers low-pressure steam systems. Insulation starts at 1.5 inch for any size up to 1-1/4" pipe size. For what are common LP steam main sizes in these parts (2-inch pipe size generally serves a dwelling unit or single family house) then 2-inch insulation thickness is indicated. You can use the 1-inch thickness where it makes sense to fit it ("better than nothing"). But at least you will know how far from code you will be.

You may have to order through a commercial supply house to get the correct sizes and thicknesses; the box home improvement stores stock limited thicknesses and pipe sizes.


Hope this helps!

Sarah Johnson

Thanks for all the suggestions! They are all very helpful.

Pete_18

Thanks

Brad, thanks for the additional info on code. I can only imagine how much 1.5-2 inch thick fiberglass insulation costs

At my local plumbing supply store, the General Insulation cost per 4 feet of 1 inch thick fiberglass insulation for my 3 in. main ran $13 a piece. Of course my discount probably stinks compared to what a plumber gets.

I was very pleased with the results, my basement was about 90F and is now freezing and I can no longer feel any heat through the 1 in. fiberglass. The 1/2 in. is minimal, but it was all I could fit and I figured it was better than nothing on the risers to each radiator.

Brad White_10

You did well, Pete!

We have a saying that "the first inch does all the work".
Let me give an example.

Say you have a foot of bare 2-inch pipe at 215 degrees (2# steam) and it emits roughly 150 BTU's per hour. (0.62 SF EDR at 240 BTUH per).

Add one inch of insulation and this drops to less than 25 BTU's per hour, a sixth that of bare pipe. Add two inches and this drops in half to 12 BTU's... the law of diminishing returns. You cut 1/6th in half to 1/12th.


Indeed the cost of thicker insulation sometimes defies proportion. I suppose the market demaind for common one-inch has the quantities higher for those sizes and keeps the cost low.

So your point is well taken and I agree that a insulation thinner than code is better than no insulation at all. And sometimes what code demands will have a cost/benefit ratio that may not seem so attractive at first. I just wanted to give a point of reference. And as an engineer, I kinda sorta have to be an advocate for the code. Well I do, not kinda sorta...

Merry Christmas!

Kevin_in_Denver_2

Elbows and Tees

The pipe insulation one sees on old steam systems has a really great looking (and obviously durable) covering. I assume it is something like asbestos impregnated plaster of Paris. Is there a updated version of this still available? (Anyone who's broken a bone knows how to apply the stuff)

I've actually used those plaster of Paris rolls from Hobby Lobby, but that's paying small-quantity-retail and it adds up quick. Is latex paint the best finish coat?

Robert Simplicio

That got me thinking

I've got one pipe in my near-boiler piping (it's actually a house cold-water pipe) that's covered in what would seem to be what you're talking about....now that's got me a little scared that I've got asbestos...but so long as I don't disturb it I should be OK. It looks to be very durable and it insulates well...but this house has galvanized water supply piping that I would like to replace with copper down the road...so it will eventually have to go. I'd hate to have to hire an abatement company for 4 feet of pipe insulation...

Brad White_9

I think that

there are exemptions for homeowners for small amounts of the A-Word material. Your local environmental department may advise you (call from a pay phone

You have to wet it down (409 detergent and water mixture) and double-bag it and wearing a ventilator mask is advised, but I have know this to be allowed. By having some reasonableness to the process it was argued that it prevented wholesale basement pipe insulation going out in the trash in the middle of the night...

Robert Simplicio

That's what I figured, but I wanted to get other views on it to be sure.