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bathroom venting and fan size

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  • #16

    Re: bathroom venting and fan size



    Brand is ultilitech. Can't find exact model, but it was 100cfm and allowed for 4 or 6 outlet vent.
    Bathroom is 50sqf
    With shower, sink, toilet, tub
    Motor is dead (no place to plug in extension, but I confirmed wiring and power directly to the motor)

    Main issue is water in the motor housing. I won't be replacing the motor, instead will be putting in a whole new unit so I can fully inspect around it.

    Main concern at this point is preventing water from accumulating again.

    Thanks and let me know if any other info would be helpful

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    • #17

      Re: bathroom venting and fan size

      I can see the possibilety of your bug screen frosting/freezing over and preventing the damp air from being properly exhausted, then the air condensing and running back into your fan, I would not like a bug screen used in the manner it is used here.

      Have fun and take care
      Leo Van Der Loo

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      • #18

        Re: bathroom venting and fan size

        Originally posted by greatness View Post

        Thanks and let me know if any other info would be helpful
        Thank you, and I apparently missed any water issues in the prior notes. You can not not have any standing water in the system. If you have any corrugated (e.g. flexible) duct, code or not, it needs to go if at all possible. Do what you can to eliminate that pair of 90's - maybe 45's?; and 4" duct should be fine to make the handling easier. Keep in mind that "rigid" galvanized duct actually has multi-segment joints that rotate so you can accommodate some odd angles. But that water shown is a critical issue for several apparent reasons.Lastly, not being familiar with your fan, probably a slightly more powerful (read cfm) fan might be beneficial.
        Last edited by Woodwreck; 02-07-2019, 05:59 PM.
        Start slow; wind down gracefuilly

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        • #19

          Re: bathroom venting and fan size

          Thanks to all. The one thing I'm not understanding: even if water is running back down the vent towards the fan, how would it get in the motor? Would it not just drip out the ceiling vent?

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          • #20

            Re: bathroom venting and fan size

            Based on your sketch, I don't think there is any way water could be running back to the fan. Assuming there isn't a plumbing leak or roof leak dripping on the fan, it must be condensation from the moisture in the air being exhausted. Two previous comments may lead to a solution. Rusty, I think commented that you need to insulate the whole fan housing and Leo suggested your insect screen may be blocked by ice causing reduced airflow and more potential for condensation.

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            • #21

              Re: bathroom venting and fan size

              Will try installing new fan, and better insulating. Going up there tomorrow to see if anything can be done about the angles/90s.

              Is there a vapour barrier boot for these applications?

              As for the insect screen, I haven't seen any freezing or water collection when I've inspected over the past few weeks (was keeping an eye on it during the high winds), but who is to say it didn't thaw after the initial issue.

              I'll look at replacing it with other screening....I notice many of the exterior vents don't have dampers and rely only on screening. So maybe larger screening(holes) is the solution?

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              • #22

                Re: bathroom venting and fan size

                See attached article, it has some good info I think. Oddly it doesn't explicitly mention insulating the fan housing but does discuss fan sizing and running the fan long enough to get rid of all the moisture from showering. I don't know if you need to add vapour barrier, I think the fan housing should act as a vapour barrier provided it is sealed to the ceiling vapour barrier.


                https://www.finehomebuilding.com/201...-cold-climates

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                • #23

                  Re: bathroom venting and fan size

                  Doug I read that article and although it doesn't mention the fan housing the pictured illustration shows it. The insulation is cut away but is certainly deeper than the fan housing so it would cover the housing. Vapour barrier over the housing is a good thing too if for no other reason than it can't hurt. Almost everything the OP did with his installation contravenes what this article says and one in particular that I mentioned in post #14 was a hooded vent that he does not have. In the OP's installation it is obvious that the fan is fighting an uphill battle and losing. Even if it could push the air up and out through the gable screen any wind at all would overwhelm the power of the fan. If he followed your article and had a straight run with no incline which would mean a new hole and hood through the gable end he would have much better performance from a rather small fan.
                  "Do it Right!"

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                  • #24

                    Re: bathroom venting and fan size

                    Exterior vents, with and without screening numerous choices.
                    https://www.homedepot.com/p/4-in-Rou...-100396975-_-N
                    Last edited by Woodwreck; 02-08-2019, 09:15 AM.
                    Start slow; wind down gracefuilly

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                    • #25

                      Re: bathroom venting and fan size

                      Thanks for the replies all.

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                      • #26

                        Re: bathroom venting and fan size

                        Here, are the vents I use on my house and they are made in Canada.

                        http://www.ventilation-maximum.com/e...-intake-vents/
                        beachburl likes this.

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