passive make up air vent
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  1. #1
    Join Date
    Jun 2008
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    58

    passive make up air vent

    I have a question for you pros, building a tight house, at least it should be. With that being said, We have designed the HVAC and going to have and ERV but with that being said. If we where to run the range hood 200 cfm max and doing a load of laundry in the dryer we would need some type of make up air. Any suggestions would be appreciated.

    One of the ERV mfgs recomended a passive unit that would only allow air in when there was a need for it. Is there such a thing like this www.skuttle.com if so, how would you install it. (not the wall portion but were would it connect to. If you put it in the return line then everytime the furnace would cycle it would suck in air over presurizing the house?

  2. #2
    Join Date
    Aug 2008
    Location
    Connecticut
    Posts
    24

    Thumbs down

    did you proof read that at all? it doesnt make a whole lot of sense

  3. #3
    Join Date
    Mar 2008
    Location
    Central Maryland
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    246
    Quote Originally Posted by Blacklabelman1 View Post
    did you proof read that at all? it doesnt make a whole lot of sense
    Makes perfect sense to me.

    OK, he should have used "where" instead of "were", and "an" instead of "and" (a common keyboarding error).

    From the web page description: "When the furnace blower operates, the air control damper opens, automatically drawing outside air into the furnace. "

    ...it seems that it connects to the Return near the furnace.

    -HF

  4. #4
    Join Date
    Aug 2008
    Location
    Connecticut
    Posts
    24
    ohh i see now haha, fan in a can is always an option

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,595
    Hook it up the way they say. Its designed to give you a slight positive pressure.

    You set it up, so the damper only opens ½ way with the blower running. And no other exhaust devices running.
    You could set it to open less if needed.
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  6. #6
    Join Date
    Apr 2002
    Posts
    11,808
    normally if I had sealed combustion furnace/water heater I would not worry about it.

    get a six inch intake hood with a 120V motorized damper. It opens when the range hood runs. Let it spill air in the basement somewhere away from water lines


    I never worried about the intermittent things unless you really had something tight like an R2000 home and were installing a jenn air down draft grille or had the large designer kitchen hoods.

  7. #7
    Join Date
    Jun 2008
    Posts
    58
    My concern with just letting it dump into the basement. Is that the basement is finished and you would not want to dump hot humid summer air in.

  8. #8
    Join Date
    Jun 2008
    Posts
    58
    anybody else???

  9. #9
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    When you're doing a load of laundry in the dryer and running the range hood - crack a window in the kitchen.

    Synical? Yes. Cheap and really obvious fix to your quandry? Also yes.

    How much negative pressure do you think a 1/15 hp fan can produce? We are not talking about sucking the doors off their hinges here!

  10. #10
    Join Date
    Jun 2008
    Posts
    58
    im more worried about the dryer, I was told it is acouple 100 cfm during each cycle

  11. #11
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    Quote Originally Posted by acnoob1 View Post
    im more worried about the dryer, I was told it is acouple 100 cfm during each cycle
    What are you worried about? I'm assuming you have a direct vent furnace/boiler and hot water heater - so there is really no danger or problem being created. This negative pressure you speak of will be impercievable, and if it is, crack a window when both aplliances (dryer and range hood) are on.

    This is no big deal - a cracked window will alieviate any pressure differences if the house is truely that tight. It doesn't have to be in the same room.

    There are commercial buildings out there with thousands of cfm's being sucked out with little or no make up air. That's when it's a problem - 200 cfm is piddly winks in a whole house.

  12. #12
    Join Date
    Jan 2008
    Posts
    85
    Quote Originally Posted by acnoob1 View Post
    im more worried about the dryer, I was told it is acouple 100 cfm during each cycle
    The numbers I've seen for clothes dryers are all too high. Here's a link to Wisconsin
    study that measured their CFM. Low of 20, high of 97, average 54 cfm.

    http://www.ecw.org/download.php?prod...prod/216-1.pdf

  13. #13
    Join Date
    Jul 2008
    Location
    Denver, CO
    Posts
    4,229
    Here is my thoughts on the subjuct. Any new tight house needs to beable to get fresh air in from the outside. In my opnion completely sealing off a house from fresh air is a bad idea. I recommend looking at installing a makeup air unit with a air to air heat exchanger. This will either heat or cool the fresh air comming in from the out side and also has a filter installed.

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