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Insulating mains and dry returns

amitjm1980 Member Posts: 33
edited February 2019 in Strictly Steam
After a new boiler install, i'm considering insulating my steam mains and dry returns. Currently it's the only heat in the basement and I have no idea if any of the ambient heat from the boiler itself would keep it warm enough to be comfortable and to help stop pipes from freezing in extreme temperatures (it's unfinished, but our laundry machines are down there). I'm thinking no and i'd need some auxiliary heat. Any recommendations? Anyone have experience with these? Also, anyone have any math or examples on cost savings on insulated vs uninsulated mains?



  • Jamie Hall
    Jamie Hall Member Posts: 21,541
    The steam mains should definitely be insulated. Most folks recommend 1 inch fiberglass insulation. Dry returns are another question. There are two very different things often referred to as dry returns: one variety is simply an extension of a steam main -- continuous pipe -- coming back to the boiler. Those should be insulated just as though they were steam mains, since in reality they are (they should also be vented). The other is found on two pipe systems, and are true dry returns -- that is, they are not directly connected to the steam mains, but separated by traps if they are connected at all. If things are working properly, they should never carry steam and they need not be insulated.

    On heat in the basement -- the steam mains dump very little heat, and that mostly at ceiling level. I'd not worry about it until you've lived with it for a while and find out how your basement responds.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • amitjm1980
    amitjm1980 Member Posts: 33
    @Jamie Hall My dry returns are an extension of the main, so I'll need to insulate them also. The main vents are at the end of those, just before they drop down and transition into the wet return. That's a good point about dumping very little heat. I guess I should just insulate and see what happens. Worst case I'll use a space heater if it gets too cold until I can remedy the heat.
  • gfrbrookline
    gfrbrookline Member Posts: 727
    I went without insulating the for a long time then bit the bullet and wrapped them. It did make a big difference, helped with overall balance and the rads heated faster.

    Don't waste your money on the HD stuff. Go to buyinsulationproductstore.com, much better quality. You need 1", the HD stuff is 1/2" at most. Make sure to insulate the corners as well.