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Bathroom exhaust fans with positive closure dampers

Discussion in 'Environmental Discussion' started by richard schumacher, Oct 2, 2008.

  1. richard schumacher

    richard schumacher shortbus driver

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    I'm trying to find a bathroom exhaust fan that includes an electrically-operated positive-closure exhaust damper (air valve). All the fans I've found so far rely on passive weighted dampers; in the high winds we commonly get here these pop right open whether or not the fan is operating, creating a three or four inch hole in the ceiling.

    The state of Oregon mandates low-infiltration ceiling light fixtures so I thought they might be able to provide a pointer, but no.
     
  2. Bob47

    Bob47 New Member

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    I have only seen those kinds of dampers on rather large attic fans. What about using a turbine vent cap? These are made for RVs, motorhomes in particular, so they can operate while in motion and are capable of dealing with very high wind speeds. If you have very cold temperatures during the winter it might not be as good as a weighted damper, but would probably work in moderate winter climates.
     
  3. jayman

    jayman Senior Member

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    Here in Canada, it has been common for +4 years to build homes with central exhaust ducting, which runs through a central exhaust blower or a Heat Recovery Ventilator

    My home and hobby farm home have extractor vents in the kitchen, all bathrooms, basement (Radon mitigation), and laundry room. The variable speed furnace fan is always on low, and the HRV is always on low.

    This ensures a constant supply of fresh air in the home. If taking a shower or cooking, you hit the switch to engage high speed for 15 mins. The better HRV's have frost sensors, once frost is detected in the unit, a damper is closed and the unit operates in recirculation until the frost is gone.

    That is far cheaper to operate than units with electric defrost options

    I don't know of any residential exhaust fans with positive-close dampers
     
  4. richard schumacher

    richard schumacher shortbus driver

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    Thanks, I'll keep HRVs in mind if we ever remodel.
     
  5. jayman

    jayman Senior Member

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    One advantage of building a home with central exhaust: anytime in the future you can upgrade to an HRV. You just remove the central exhaust blower, run that pipe into the exhaust port of the HRV, and run the fresh air supply into the cold air return ductwork.
     
  6. sparkyAZ

    sparkyAZ übergeek

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    You might have to do some creative ductwork, but there are some options. I think your best bet would be to buy a standard fan and install an electrically operated duct damper inline with the exhaust. You can get electrically operated duct dampers here:

    "damper" - Smarthome

    The smallest diameter available is 6" so you may have step up your duct diameter then back down again. Also, the actuator is 24vac so you have to wire a transformer into the fan electrical circuit to open the damper when the fan is switched on.
     
  7. hyo silver

    hyo silver Awaaaaay

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    What about putting a small magnet on the flap, and a metal washer on the vent? The right size would keep the flap shut, yet still release with the pressure of the air flow when the fan's turned on.
     
  8. Sufferin' Prius Envy

    Sufferin' Prius Envy Platinum Member

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    The best one I ever saw was an inline box half way up the vent pipe.

    The flapper was one of the four walls of the box.
    When the fan was off, the flapper would drop to about a 25 degree angle and open the flapper side of the box to the attic. The attic gets ventilated and high winds fail to lift the flapper because it sucks out attic air rather than creating a vacuum to lift the flapper.

    Turn on the fan and the flapper rises and becomes the fourth wall of the box, thusly venting the bathroom humidity and smells outside and not into the attic.

    Where you would get one, I don't know . . . I saw it quite some time ago.
     
  9. thedutchtouch

    thedutchtouch prius is my SUV

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  10. darelldd

    darelldd Prius is our Gas Guzzler

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    What the heck is up with those plastic dampers? Insulate the whole dang house and caulk around everything that holds still... and then you have these giant holes to the outside air? Crazy! I'm with you there! This isn't rocket science. I don't even understand why they're legal they way these are sold.
     
  11. Sufferin' Prius Envy

    Sufferin' Prius Envy Platinum Member

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    That's why I have all four bathroom walls insulated (one is an outside wall). I open the window, turn on the exhaust fan, close door. Only the bathroom is subjected to heating up or cooling down to the ambient outside temperature, rather than sucking mass quantities of conditioned air from the rest of the house . . . but well before then, the moisture is gone. Then I just close the window and open the door.
     
  12. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    i guess kid too young, around here, no one ever closes the bathroom door so ventilation not needed... but it is an advantage with 3 bathrooms so just use the one that is most private at the time if needed.

    i shower most of the time when no one else is up...either at 5 am or after 10 pm...so no biggie
     
  13. richard schumacher

    richard schumacher shortbus driver

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    Yeah, one would think so, and that's what I've been doing off-and-on for four years. If there's an aluminum unit (it's for bathroom exhaust, so steel would rust away) out there less than 8" diameter that costs less than $150 I have not found it.
     
  14. sparkyAZ

    sparkyAZ übergeek

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    Ok, here's what you do:

    1.) get some inspiration by watching an episode of the Red Green show. It really does not matter which episode you watch, but pay attention to the creative use of Duct Tape. This will come in handy in step 4.

    The Red Green Show

    2.) Order one of the sheet metal dampers from the various sources.

    3.) Remove the damper motor gizmobob with the assistance of a large flat blade screwdriver. Improvised techniques work best for this step.

    4.) Attach the damper motor to the cheap plastic unit that came on the expensive but motorized-damperless fan you bought at the home improvement store. See step 1.

    5.) problem solved! The women should definately find you handy!

    Another option:

    Find a friend who is into flying radio controlled aircraft. Hang around the airstrips until one has an "uncontrolled gravitational experience". Out of the wreckage, harvest a servo motor. Proceed from step 4 above.
     
  15. bfr

    bfr Techno Nerd

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    Sorry to drag up this old topic. Found it in a search and thought others might still be looking for a solution. Living in Jackson Hole, WY I get plenty of 20 below type of weather with strong winds. My little plastic flappers do squat and subsequently I have freezing cold air in my bathrooms. Ridiculous really. So this summer I am addressing the issue. The best product I found for my situation is from American Aldes.

    These backdraft dampers insert right into the ductwork, sealed tight and quiet by foam gaskets. They are "positive closure" in the form of spring loaded butterfly dampers that require .04 to .08 inches W.G. (pressure) in order to begin to open. In the closed position the dampers seal up against EDPM rubber gaskets that are designed for temperatures from - 22°F to 180°F. I needed the 4" size but they come in sizes all the way up to 16" commercial duct work.

    Hope this helps someone else seal up their leaky bathroom fan ductwork. The mfr site is American Aldes dot com. I was able to find them at Bathroom Fan Experts online.