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Does anyone know of a good 12x12 vent for a boiler room that can be shut sometimes when cold out?

Joseph_4Joseph_4 Posts: 198Member
I have a customer where the boiler is being built on the second floor. The boiler room is right on the external wall and the inspector wants a 12x12 opening at the top of the room and a 12x12 opening at the bottom of the wall in the boiler room. The pipes are a few inches away from the outdoors and I am concerned that if I put a regular vent, then on a freezing cold day the pipes might get too cold even though I am going to put fiberglass insulation. Is there a kind of vent that anyone knows of that has a shutter that can be closed or even somewhat closed on a very cold day?


  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    Danger! Danger!
    If you need the vents for combustion air, then you really need the vents when it's cold or you'll starve the unit for combustion air and could create either a backdrafting and/or high don't close it off.
    What type of boiler is this (make/model)? Maybe you can bring combustion air right into the unit and forgo the openings.
  • SlamDunkSlamDunk Posts: 696Member
    edited September 2019
    Yeah, you need so many sq inches of outside air opening per mbtuh for combustion. We have an entire outside wall open to the outside and had to heat trace and insulate all pipes. Insulation without heat traces are not helpful.
  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    Although a good article, the OP is looking to close them when it's cold and the unit needs to run.
    So that may help a little, but more info about the boiler and can combustion air be brought directly into the boiler would help.
  • SteamheadSteamhead Posts: 13,510Member
    Maybe a duct from the opening to near the boiler, with a motorized damper as described? This could get the cold air away from the pipes.................
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • JUGHNEJUGHNE Posts: 6,441Member
    Could you consider the "Fan in a Can"?
  • Joseph_4Joseph_4 Posts: 198Member
    Its a Green Mountain GMPVB series 2 induced draft boiler 150k input.. Once the Village inspector asked for it.. i need the 12 by 12.. should I not be worried about the very cold?
  • STEVEusaPASTEVEusaPA Posts: 3,691Member
    With that boiler it looks like leave the openings, but @JUGHNE 's idea of a 'Fan in a Can' and no openings is probably the best idea.
  • Jamie HallJamie Hall Posts: 11,889Member
    Joseph_4 said:

    Its a Green Mountain GMPVB series 2 induced draft boiler 150k input.. Once the Village inspector asked for it.. i need the 12 by 12.. should I not be worried about the very cold?

    You certainly should do something about the possibility of the cold freezing the pipes.


    That does not include shutting off the required combustion air for the boiler. Doing so will create a very dangerous -- quite possibly fatal -- condition, and you really don't want to do that.

    Creating fan assisted, closed combustion air and exhaust is one option -- but if you are going that route, it has to be done right, so there is no possibility -- none -- of combustion gas getting into the house. Unless the boiler and burner system is designed for it, that is, to my mind, a rather iffy option.

    Another would be to reroute the problematic plumbing so it isn't in the same space as the boiler.

    Another would be to heat trace and insulate the piping.

    I'd prefer rerouting the problematic plumbing, myself.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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