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Steam Pipe Insulation - Recommended type and sources.

Presently, none of my steam piping in my parrallel flow one pipe residential system is insulated, and yes my basement gets very toasty. The near boiler piping, header, equalizer, and take-offs are Copper appear to be 3" near the comparatively newer boiler (installed in 1989) leading to 3" horizontal black pipe mains that lead to approximatley 1 1/2" to 2" black pipe risers and cast iron radiators. I don't have calipers to measure the O.D. and I understand that insulation is often specified by pipe type and I.D. just to confuse the matter. I'll need to measure the circumference and figure from there, WHEN THE PIPES ARE COOL! Burnt my inner arm this morning trying to determine if the Hoffman 75s where working properly at the end of the returns, HOT! Not sure how to tell if these main vents are working well, that is venting the system quickly and then closing all the way when the steam is present. One was still venting slightly even though the return below the nipple riser was to hot to touch, OUCH, the other two Hoffman 75s on the other two adjacent returns were not noticeably venting hot steam / air.

I am looking for advise as to the type of insulation and sources for insulation to install on the horizontal mains and risers which are located in the basement and crawl space of my 1895 Victorian home. The pipes leading to the second story are mostly in the walls are not accessible, with one or two exceptions which could be insulated as they run on the interior of the rooms.

Could one use the closed cell (split seam neoprene style) material as it would seem to be the easiest to install?
Wrapping pipe in a crawl space is not fun what with all the loose dirt and overhead activity. Will the closed cell polymer sustain the high heat with out melting? I don't want a gooey mess on my pipes from melted polymer insulation. Do they make closed cell insulation for large pipe sizes? All I have found in the usual hardware stores is for insulating the typical domestic supply water pipes, 3/8 to 1", which operate at much cooler temps. than steam pipes? If so, can you please provide sourcing information so that I can order the "floaties" or "noodles". My daughter will really like the oversized versions when swimming in the lake.

Please note: The closed cell type of insulation has the added benefit of being cushy which softens the impact of one's head against the low slung returns and mains in the already low ceiling of the basement of my Victorian. When one had to dig the basement and foundation by hand I guess one didn't go any deeper than absolutely necessary, to the frost line, 6 feet down. I can sympathize with that labor task but my head regularly regrets the lack of additional clearance, especially in the dark. Thud, *@#%!!!! Glow in the dark insulation would be really good for my thick skull.

What thickness of insulation or R value would be appropriate?

Also, should I discontinue insulating the one pipe system just after the last riser so that the return piping can cool and condensate prior to reaching the main air vents which are located at the end of the dry returns just before the steep drop to the short length of wet return just before the Hartford loop and second drain / clear out valve? What happens in a system if the steam does not condensate sufficiently until it gets near the main vents risers and the steep down drip to the wet return? My question and issue is where to stop insulating the pipes?
Also, I suppose I need to know where should I start insulating the pipes, at the header? at the take offs? and should the equalizer be insulated? Lots of questions, but often the devil is in the details.

Lastly, will the reduction in pick-up from insulating the mains and the few accessable risers to the second story, (most of the risers to the first level are accessible from the basement and crawl space) potentially impact adversely the operation of the boiler, that is perhaps cause the boiler to then become oversized?

I am hoping for efficiency gains, and not inadvertently adding mechanical difficulties from reducing the pick up drastically. You know, change one thing for the positive and perhaps change another to a negative. I suppose if the reduced pick up causes short cycling, or other difficulties, I could add offsetting load, like finishing out the unheated, unfinished huge attic or perhaps heating an outdoor hot tub (that would be a cattle trough in Montana), add an indirect domestic water heater, heat the outdoor dog houses (my thin coated basset hound would favor that on a cold winter night) or maybe underfire the boiler somewhat, but not too much.

By the way, that is how we dispose of the excess electricity generated by our hydroelectric plant at our mountain property; we dump the extra load into large heating elements placed in a large galvanized cattle trough and pipe cold mountain stream water continuously into the cattle trough to keep it from over heating and becoming scalding hot. You adjust the temperature to one's desired comfort by regulating the amount of incoming cold water from the adjacent stream. One needs to over generate electricity in such a basic remote system so that when the refrigerators kick on the lights don't noticeable differ, or the voltage spike and drop a lot. This is not a good system for sensitive electronics, no computers. We also leave all the lights and space heaters on night and day, putting the space heaters outside in the summer, else the cabins get way to hot. Unlimited energy and water availability. One needs to adjust habits upon returning to town and remember to turn the water off and the lights out, else the utility bills get a bit out of line.

My Victorian home in town has the typical rock foundation walls and yes there are some air gaps around the perimeter as one would expect from settling. (I'm strongly considering having the perimeter sprayed with the closed cell insulation to close up the small gaps to avoid the obvious heat loss and drafts under the house). Maybe insulating the pipes and insulating the foundation perimeter will provide the heat loss reduction along with the pick up reduction so that the basement stays comfortable, not to hot, not to cool. We'll find out when it gets cold this winter.

Thanks for your input. I don't know much about steam except having learned recently that it is very hot, too hot to touch. But I learn quickly, probably won't burn myself but a dozen more times. From the Last Best Place, Dillon, Montana.


  • Al Letellier
    Al Letellier Member Posts: 781
    steam pipe insulation

    Don't use close cell insulation....it will melt.
    Generally speaking, we use 1" thick fiberglass to insulate steam mains and runouts. It won't adversely effect boiler operation unless you've got miles fo piping. Insulate every piece of piping above the water line fo the boiler and you'll be safe and efficient.
    Your best overall bet is to hire a pipe insulator. Often times they can provide and install the stuff for about the same amount of money you will spend to buy it, so why bother doing it yourself....and it will look llike a pro did it.
    There is a shortage of insulation on the market and you may have to resort to an insulating contractor just to get the stuff.

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