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  1. #1
    Join Date
    Mar 2009
    Posts
    237

    Default Fresh Air Intake Valve

    I currently introduce fresh air into the house by leaving a basement window cracked open. This helps me feel confident enough combustion air is being introduced for the boiler and hot water heater. It is a semi finished space but it obviously gets cold during the winter months and makes the floor above cold for bare feet. The boiler and water heater are now enclosed in a large utility closet and although it has the proper grills for ventilation, I want to run a pipe from outside to this new enclosed space. My hope is that this will allow fresh air to enter for combustion and if its too cold, it will help retain the cool air into this space only however I don't want to create a backdraft where heated air tries going out of the pipe instead of up the chimney. Even better would be if I could warm the air prior to entering this space maybe by running it through a copper pipe parallel to the current trunks lines of the boiler.

    Does this sound like an okay idea and are there any one-way vents I can put on the end of the pipe outside so air only comes into the home. I would assume something similar to the valve used on a homes plumbing vent would work.
    My advice and opinions come from hands on knowledge...and This Old House Hidden Content

  2. #2
    Join Date
    Aug 2007
    Location
    Maryland
    Posts
    1,520

    Default Re: Fresh Air Intake Valve

    Unless it's a new and really tight house there is usually enough makeup air to prevent back drafting down the flues from exhaust fans in the house.
    Adding an air vent to the utility room would not cause any problems. A one way damper similar to what is found on bathroom exhaust fans or clothes dryer exhaust could be added. Plumbing vents don't usually have a valve.
    Be sure to have carbon monoxide detectors in the house.

  3. #3
    Join Date
    Aug 2008
    Posts
    82

    Default Re: Fresh Air Intake Valve

    I agree with ed21; especially the part about the carbon monoxide detector and the idea that most older houses are loose enough to let adequate combustion air into the boiler room; besides, leaving a window cracked invites thieves and burglars, but you may have created what's known as a 'confined boiler room' with your new construction in regards to adequate combustion air requirements.

    The fact that you were having past problems with "cigarette odors coming from next door" may signal a problem with the boiler combustion process; go outside when the boiler is firing & check the chimney/vent to see if you see if any heavy smoke coming out (white steam on a cold day is normal); open up any inside rooms or crawl spaces in the boiler room/cellar so that you expand the volume of air available to the gas burners; nobody likes to have a boiler room open vent in winter, but they sell 12" X 9" louvers now with bug screens that are adjustable from completely closed to completely open, to 2 or 3 adjustments in between & can be temporarily easily closed on very cold days.

    Also consult your "Installation Instructions" manual that came with your boiler (you can find one on the internet if you no longer have it); the Installation manual has excellent drawings & ideas on how to vent your boiler room & how to calculate the amount of ventilation you need based on the BTU firing rate of your gas burner(s); sometime in the future you may want to include an indirect HWH for you domestic HW instead of a separate HWH---this will lessen the amount of combustion air your boiler room needs.

    Google "Confined Space Boiler Room Combustion Air Requirements" & click onto the Siegenthaler book, which also has boiler room diagrams of unique venting techniques by Siegenthaler that most people don't even think about---for example, if your boiler room can be connected to your attic, there is a way to run a 9" single wall plastic or steel tube straight to the attic so that you can access the large amount of warmed combustion air available in the attic.

    Then there are those who would love to sell you a motorized direct vent or draft inducer "Fan in the Can" for lots of dough that goes thru the nearest exterior wall for outside air.

    http://www.nationalboard.org/index.a...eID=164&ID=191
    http://www.fieldcontrols.com/pdfs/41...onAirGuide.pdf
    Last edited by dodsworth; 03-19-2014 at 10:59 AM.

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,918

    Default Re: Fresh Air Intake Valve

    What they said plus;

    The air intake must be as large a diameter as the outgoing heater vent pipe.

  5. #5
    Join Date
    Dec 2013
    Location
    Montreal Canada
    Posts
    185

    Default Re: Fresh Air Intake Valve

    Most houses have a negative pressure inside them due to dryer exhaust vents, bathroom exhaust vent, kitchen exhaust vents, chimneys exhaust. If you want to do it right then run an make up air duct from the outside to the room of the heating equipment and end it about a foot from the burners. This is a code requirement in the canadian gaz code. If a house has negative pressure all sorts of things happen like drafts inside, pipe freezing many feet inside the building. R-2000 house require positive ventilation.

  6. #6
    Join Date
    Mar 2009
    Posts
    237

    Default Re: Fresh Air Intake Valve

    Definitely not a new house but i've been doing some heavy renovation so i'm trying not to make it too tight. From the amount of cold air that i've felt inside the house this winter I know it's still breathing and the air isn't stagnant.

    dodsworth: thanks for looking at my past post relating to "cigarette odors coming from next door". I actually just updated that so while it did have something to do with missing mortar in the chimney, it was still venting properly and I did have a few contractors take a look to make sure it wasn't backdrafting. Also adding a new cap with the chiney liner must have helped for the windy days.
    My advice and opinions come from hands on knowledge...and This Old House Hidden Content

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