Bath exhaust fan venting

Discussion in 'Remodel Forum & Blog' started by dabiz7, Sep 15, 2009.

  1. dabiz7

    dabiz7 New Member

    Messages:
    42
    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. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    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.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    2,777
    Location:
    USA
    My bathroom is entirely code compliant and does not have an extractor fan.

    The window in it simply opens.
  5. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    Columbus, OH
    That's a redneck humidifier ... or was it called a house stinker? :)

    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: Sep 21, 2009
  6. FloridaOrange

    FloridaOrange Plumbing Designer

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    1,317
    Location:
    SW Florida

    Or hot. It's almost always hot here.............
  7. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
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    Location:
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    That's just greedy! Conspicuous consumption is what I call it.

    Choose a window or a fan. Not both.
  8. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    Jimbo's right.

    I am going to stop taking baths and showers altogether.
  10. hockeydad

    hockeydad New Member

    Messages:
    12
    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. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    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.
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,129
    Location:
    New England
    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.
  13. hockeydad

    hockeydad New Member

    Messages:
    12
    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. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    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.
  15. Runs with bison

    Runs with bison Member

    Messages:
    892
    Location:
    Midwest
    At least yours goes somewhere! :D 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.
  16. hockeydad

    hockeydad New Member

    Messages:
    12
    My powder room downstairs vents to nowhere as well! There is a fan, but not an outlet anywhere, so it too is just blowing air between the joists.

    Agree that so many builders will skimp where ever they can. Part of my problem was the lack of code enforcement (or codes for that matter!) in my county when the house was built nearly 20 years ago. Things are improving, but we're still way behind.
  17. toolaholic

    toolaholic General Contractor Carpenter

    Messages:
    874
    Location:
    Marin Co. Ca.
    We will all be over to Your home next week!

    How's Tue work! I would like to look at the Elec. panel 1 st.!
    As it starts,so it goes! Do the roof vents dead end in attic! DO YOU HAVE VENTS? :D GO SHARKS!
    Last edited: Oct 4, 2009
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