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Boiler Room Venting

Neil AndrewsNeil Andrews Member Posts: 14
I just finished my basement and closed off my steam boiler WM EG-45 & a 40 gal water heater from the rest of the basement with a 36" bifold door.

The room is approximately 10 x 6. The room does get rather warm during boiler operation, but I am most concerned about not having enough combustion air.

The space does have a basement window and the room is not air tight, I also have also added a vent to the rest of the basement with a standard AC return vent.

Would poking a hole through the sill and adding fresh air intake, be a good idea and provide sufficient air for the boiler?

Are special vents available for this purpose, and where can I purchase?




  • JoeJoe Member Posts: 201
    don't mess with the sill

    I mean your house is sitting on it. I think if the bifold doors were louvered that would be better (or cut a vent into them. Why bring in so much cold air into the space?
    Is the ceiling finished around the boiler? You could get air through the joist spaces if they were open somewere in the boiler room.
  • I don't completely agree

    All of the air that the boiler and water heater use comes from outdoors. Bringing it directly to the boiler room, instead of throughout the house, eases the infiltration in the rest of the building that is caused by these appliances.

    The size of these grilles is specified in your boiler manual. Closing in the boiler area must meet building codes AND fuel gas codes. This isn't optional work, and the air openings are required. If the boiler is in a confined space, the rules change from being in an unconfined space. Be very, very careful. There is risk of carbon monoxide being created and released inside the building, if the air supply isn't right.

  • EricEric Member Posts: 95
    Combustion air

    Follow the code. Combustion air is very important. Direct connections to the outside are typically prefered. Combustion air is infilation if you dont provide an opening. In our cold region a local amendment to code allows for engineered combustions openings in conjuction with a cooling ventilation system.
  • Neil AndrewsNeil Andrews Member Posts: 14

    Thanks for your input Noel.

    The space was approved by an inspector who suggested that a vent be placed to the remainder of the basement, which is currently in place.

    Again this is not a tight room & the ceiling is not closed in. A wired carbon monoxide detector is also installed in the space and has never gone off.

    What I am looking to do is to suppliment the current combustion air being drawn from the basement with some fresh air from outdoors.


  • hot rodhot rod Member Posts: 1,387

    1 sq. inch of free air space in the grille for each 1,000 Btu's of combustion gross input & that's to be for each of two grilles - one upper (roughly 5 to 6' above the floor & the other closer to the floor level).

    There are also formulas for cubic footage of indoor space, but once you close off the equipment you'll need to accomodate the need for combustion air. If not, you'll increase the production of CO & sometimes quite dramatically.

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  • Mad DogMad Dog Member Posts: 2,595
    Sorry, Joe but that is Bad advice

    and before I took The Carbon Monoxide certifications with Jim Davis of National Comfort Institute, I wasn't sure either. Properly sized supply and return ducts from the outside to the boiler room will not make the boiler room excessively cold. Proper circulation of air and proper air for combustion are key here. If the room is not properly fed and vented with fresh air, the equipment will draw from the rest of the house and living area - not good. Don't even get me started on "co detectors"....The home depot specials, i.e. Kidde Nighthawk, et cetera don't sound off until very high and dangerous levels of 70 ppm are reached. There is only one brand I would have in my house or sell to customers: CO EXPERTS - starts reading at 1 ppm...beeping at 10 ppm!!!! and it keeps a record of When the CO problem occurred!!!!!!especially with today's "tighter" homes, situations can be created where a fan in the house with draw the air out of an unvented boiler room, drawing CO and other combustion products in to the living space. Additionally, most plumbing and building inspectors - forget about home inspectors (except Arlene - the most caring home inspector on earth!!!),don't have the first clue about combustion, co, or air balancing. Mad Dog

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  • LarryLarry Member Posts: 86
    Confined space

    You haven't mentioned the combined btu rating of the equipment. A minimum of 50 cubic ft. volume per 1,000 btu is required to be able to use all combution/ventilation air from indoors. Any less than that is a confined space and provisions can be made in several ways to make up the deficit. Openings can be made to adjacent spaces keeping in mind the combined volume satisfies the minimun requirement. All air can be brought in from outdoors, or a combination of indoor and outdoor air can be used. There is a formula in the International Mechanical Code for this but it's a little confusing. They compute using ratios.

    Happy ventilating.

  • I am getting in a little late

    on this. The new National Fuel Gas Code has several methods of getting "Air for Combustion" into a space. If you will give me the BTU ratings on your equipment and the flue sizes I will give you several alternatives. I also have a manual on this which explains all of the details on how to figure Air for Combustion. It is also important to check with your local inspectors as to what they will allow. You also want to be sure that you have adequate clearances to combustible materials.

    It is important to make note of the fact that the new NFGC has changed the way you figure air for combustion. The area of the country you live in may determine what code applies. Let me know all of that and I will give you several alternatives.

    Look forward to serving you.
  • mickeymickey Member Posts: 13

    Whatever ducting method you use you MUST allow for grill restriction,wood grills only allow 25% airflow and metal allow 75% airflow unless you use mechanical venting.Also you should never put a return vent by a boiler. Mick
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