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  1. #1
    Join Date
    Sep 2007
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    4

    Default Furnace Room's Fresh Air Intake Comes From Attic

    I see that the ducts for the fresh air intake for the furnace room go up to the attic and pull the air from there. There is no filter on the ends of the ducts. It seems to me the ducts shouldn't end in the attic this way. I would think that this will cause them to pull in dust and particles from the attic into my heating/cooling system and then pump that into the rest of the house for us to breathe...

    It also seems to me that if it pulls the fresh air from the attic, it would pull hot air in the summer that needs to be cooled by the AC, and cold air in the winter that would need to be warmed...

    Is this normal and I'm just off base, or should it be fixed?
    If it should be fixed, should I just put some sort of filter on the open end of the ducts in the attic, or should I reroute them to pull fresh air from outside? Where?

    Thanks

  2. #2
    Join Date
    Aug 2007
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    21

    Default Re: Furnace Room's Fresh Air Intake Comes From Attic

    No, this is not normal.
    The usual route for a fresh air intake is off of the cold air return to the outside wall of your house.
    Have an hvac contractor cap the duct in the attic off and creat a proper fresh air intake.
    Last edited by Graphite; 09-06-2007 at 05:59 PM.

  3. #3
    Join Date
    Sep 2007
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    4

    Default Re: Furnace Room's Fresh Air Intake Comes From Attic

    OK, I appreciate the feedback. I'm glad I got curious and poked around up there. I'll get an HVAC guy involved.

    From what I've now heard I'm just shaking my head. We're the 3rd family in this house. I would think that at some point someone would have caught this. We've been in the house for a few years now, so my only recourse is to bear the cost of fixing it.

    I'm going to try to post a couple photos I took last night, so you can see what I'm talking about. If these work, you'll see that the fresh air intake comes up about 3 feet into the attic and stops with openings right next to stacks of insulation, both rolls and blown. There is a master bedroom, with a vaulted ceiling directly beneath the rolled insulation in the photos.

    I easily verified that these go straight down to the furnace room. I turned on the light down there and had my daughter wait down there while I went up top. I could hear her and see her foot in the light at the bottom end.

    Notice that the insulation is bulging over the rim of the fresh air ducts. When I checked the furnace area, I did find a clump of insulation down there that I probably inadvertently knocked down the duct while I was moving around up there. (I've not seen a clump down by the furnace before.)

    The other photo I'm trying to attach shows the "dent" of a hole that was made for one of the rooftop vents. There were three of these. None of them were big enough for me to stick my hand through. I've fixed two, by cutting them wider. This third one is hard to get to, but I plan on having it fixed as well.

    Thanks again for the advice in response to this original posting and the other posting about insulation...
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  4. #4
    Join Date
    Aug 2008
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    1

    Default Re: Furnace Room's Fresh Air Intake Comes From Attic

    Wait a minute. In most houses the "furnace fresh air supply" is strictly for combustion air, to make sure your furnace doesn't get backdrafted because of other exhaust fans in the house. The furnace doesn't really move that air around to the rest of the house. Do you have a special situation here where it is actually "sucking in" fresh air for the ventilation system through these vents?

    You can test this by checking the airflow through the vent both when the flame kicks on and when the fan kicks on--if the airflow is about the same then this is just a combustion air supply. If so, there's nothing wrong with this venting arrangement, assuming your attic does have vents to the outside like most do. However, I would extend that vent above the insulation to make sure it doesn't get covered, and I'd put a screen on both ends to stop bug migration (your attic vents should be screened anyway, but JIC!).

    Actually if this is just combustion air it isn't such a bad idea. Usually there's a vent direct to the freezing outside air, and pulling that in usually makes your crawl space or furnace room pretty cold. The attic should be warmer most of the time--and the air movement should help keep your attic insulation dry. (All this presumes that there isn't a fire danger related to this vertical vent.)

  5. #5
    Join Date
    Aug 2007
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    Default Re: Furnace Room's Fresh Air Intake Comes From Attic

    Quote Originally Posted by EricTheRon View Post
    Wait a minute. In most houses the "furnace fresh air supply" is strictly for combustion air, to make sure your furnace doesn't get backdrafted because of other exhaust fans in the house. The furnace doesn't really move that air around to the rest of the house.
    A portion of that air could be drawn into the furnace through the return air connection at the furnace.



    You can test this by checking the airflow through the vent both when the flame kicks on and when the fan kicks on--if the airflow is about the same then this is just a combustion air supply. If so, there's nothing wrong with this venting arrangement, assuming your attic does have vents to the outside like most do. However, I would extend that vent above the insulation to make sure it doesn't get covered, and I'd put a screen on both ends to stop bug migration (your attic vents should be screened anyway, but JIC!).
    This setup could contribute to increased negative pressure within the home and surely will ceate a negative pressure in the attic space which would upset the attic venting.
    Also drawing fibers from the insulation down into the living space.... which is not a good thing.

    Actually if this is just combustion air it isn't such a bad idea. Usually there's a vent direct to the freezing outside air, and pulling that in usually makes your crawl space or furnace room pretty cold. The attic should be warmer most of the time--and the air movement should help keep your attic insulation dry. (All this presumes that there isn't a fire danger related to this vertical vent.)
    The outside air is considered "fresh air" ... somehow I have a hard time believing this would be allowed.

    I'd be curious if this wouldn't violate a fire code since it is open from the basement to the attic.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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