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Thread: Bath exhaust fan venting

  1. #1

    Default Bath exhaust fan venting

    The geniuses that built my house connected the exhaust fans in both of my bathrooms to the cold air return tubes in my attic space. Is it ok to do that? Does not seem right to me.

    I would like to install new fans and when I do, would like to create a manifold with 4" duct and connect both fan's exhaust to a my drier vent stack going out the top of the roof. Does that sound lile an acceptable idea? Not sure if code will accept that.

    Great forums!

  2. #2
    Plumbing Designer FloridaOrange's Avatar
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    As far as I know you cannot connect the bath exhaust with the dryer. Take them out ot their own termination point.

    Exhaust into your return.........unreal.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  3. #3
    Plumber jimbo's Avatar
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    A dryer exhaust should not be shared with anything. It also should not go out through the roof. Unless you have a booster fan, the dryer performance and energy efficiency will be lousy.

    Combining 2 bathroom exhausts can also be trouble. If hooked up wrong, one will backfeed the other. Because the high moisture in the bath exhaust, it should also not go where you say it does.

  4. #4
    Senior Robin Hood Guy Ian Gills's Avatar
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    My bathroom is entirely code compliant and does not have an extractor fan.

    The window in it simply opens.

  5. #5
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Quote Originally Posted by dabiz7 View Post
    The geniuses that built my house connected the exhaust fans in both of my bathrooms to the cold air return tubes in my attic space.
    That's a redneck humidifier ... or was it called a house stinker?

    Quote Originally Posted by Ian Gills View Post
    My bathroom is entirely code compliant and does not have an extractor fan. The window in it simply opens.
    I like both a window and a fan. Shut door, open window, turn on fan.

    Problem is people don't open the window--especially when it's cold.

    (When I remodel the bathrooms in my rentals I'm going to put the fan on a timer so that whenever the light comes on the fan comes on and stays on for a few minutes. Sucks when you're in for a sec to take a leak, but it will keep the room ventilated. Not many people know to turn the fan on when they shower. )

    Jason
    Last edited by Lakee911; 09-21-2009 at 02:40 PM.

  6. #6
    Plumbing Designer FloridaOrange's Avatar
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    Quote Originally Posted by Lakee911 View Post
    Problem is people don't open the window--especially when it's cold.

    Or hot. It's almost always hot here.............
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  7. #7
    Senior Robin Hood Guy Ian Gills's Avatar
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    I like both a window and a fan.
    That's just greedy! Conspicuous consumption is what I call it.

    Choose a window or a fan. Not both.

  8. #8
    Plumber jimbo's Avatar
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    Quote Originally Posted by Ian Gills View Post
    That's just greedy! Conspicuous consumption is what I call it.

    Choose a window or a fan. Not both.
    In my experience, people who have a window don't open it..either it is stuck, or they keep it closed for privacy.

    And people who have fans don't run it because it is too noisy!

    What a country!!!!!!

  9. #9
    Senior Robin Hood Guy Ian Gills's Avatar
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    Jimbo's right.

    I am going to stop taking baths and showers altogether.

  10. #10

    Default two fans one soffit vent?

    Regarding connecting two exhaust fans to the same soffit vent:

    I was planning to do this. Both fans have a flapper valve (not real tight - I know), plus I bought seperate flapper valves that I intend to install on both lines just prior to a Y fitting. These flapper valves seem to shut pretty good. Should I not do this?

    The vent will be coming out in a noticable location on the soffit, so I didn't want two vents. Thanks.

  11. #11
    Plumbing Designer FloridaOrange's Avatar
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    Quote Originally Posted by hockeydad View Post
    I was planning to do this. Both fans have a flapper valve (not real tight - I know), plus I bought seperate flapper valves that I intend to install on both lines just prior to a Y fitting. These flapper valves seem to shut pretty good. Should I not do this?
    The motors in most exhaust fans are pretty small and operate under minimum static pressure hence the weak flappers (backdraft dampers). If you do what you describe try getting a higher cfm rated unit than you would typically need, but that's no guarantee.


    If I were worried about backdraft I would try to install it so there isn't a short run of duct to on or the other from the Y.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    Personal opinion, soffits are a lousy place to put your exhaust vents. The goal is to keep the moisture out of the house. A proper soffit is like an intake manifold...it sucks air in to ventilate the attic and exhaust out the ridge (or other) vents in the house. Thus, sucking most of that moisture right where you don't want it. Especially problematic in a wold climate where it can condense, freeze, and create all sorts of problems on the underside of the roof decking - plus, possibly adding moisture to the insulation, rendering it much less effective.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  13. #13

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    Hmmm. I figured anything would be better than what I had. The old fan from the hall bath vented straight in to the attic (idiot builders) and there was no fan in the master bath (and no window, either). I added a fan to the master and remodeled the hall bath and am finishing off the vents.

    I really don't want to mess with going through the roof, so would going out a vertical surface on the side of the house from the attic, many feet away from the soffit, be recommended?

  14. #14
    Plumbing Designer FloridaOrange's Avatar
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    As you said, anything else besides what you have would be better.

    I understand the concerns of venting at the soffits but mine are like that and have been for 10+ years without issues.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  15. #15
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by hockeydad View Post
    Hmmm. I figured anything would be better than what I had. The old fan from the hall bath vented straight in to the attic (idiot builders) and there was no fan in the master bath (and no window, either). I added a fan to the master and remodeled the hall bath and am finishing off the vents.
    At least yours goes somewhere! The builder of this home had one fan that "vents" in between the joists...but has no connection to the outside. The only path for the air is back to the utility room.

    Two others vented into the insulation of the attic, they had no ducting and I had to dig through insulation to find them. So I was happy just to get them vented into the attic space at last.

    The stuff that builders get away with is amazing.

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