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Community and Q&A

Motorized Damper for Bathroom Exhaust

anonymoususer | Posted in Mechanicals on

We recently purchased a bathroom exhaust fan that we like very much: Nutone 9093wh. Exhausts 70 cfm. Problem is, during our harsh New England winters, the flimsy plastic louvered wall cap blows open closed open closed open closed with each puff of the wind, letting in heaps of cold air. We would rather thin our wallet and buy a motorized damper that will open when the fan motor is running, then close tightly once the motor shuts off. What brand/model do you recommend? Exhaust fan is installed roughly 5 ft from the wall. Straight shot out (no bends). 4 inch circular duct. Nutone does not make motorized dampers for exhaust fans (or so they told us by phone). We found the following product and wrote the manufacturer to ask if it might be compatible, but so far no response:

Another question: because we are so pleased with this exhaust fan, we are contemplating buying the same model for our laundry and maybe our kitchen. Does anyone know if building codes require exhaust fans in laundries? Not sure if this makes a difference, but the clothes dryer we just ordered (supposedly will deliver in June) is electric ventless heat pump, and kitchen range is electric.

We live at the tristate NH-MA-VT intersection. Our local building inspsector never answers messages. Our licensed contractor said for sure bathrooms require mechanical ventilation, but he is not sure about laundry and kitchen (assuming one has range hood).

Finally, can anyone point us to a mechanical engineer willing to work on an existing home in our geographic area? Among other things, we would like him/her to carry out Manual J (we wanna switch from oil furnace to air source heat pumps). We purchased the software to carry out Manual J ourselves but would feel more comfortable paying a licensed mechanical engineer to run his/her own numbers. There are more things we need to consult him/her about, but this is one example. Thanks!

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  1. walta100 | | #1

    I think you will get a more accurate heat load from a calculation using local weather data and your fuel purchased history.


    1. anonymoususer | | #2

      Thank you, Walta. Anyone have an idea about exhaust fan requirements or about what motorized damper might work?

  2. Expert Member


    Usually the vent termination opens when there is air moving out of it due to higher pressure inside the house. If yours is only opening due to wind and admitting air from the exterior, an easier fix might be a good inline back-draft damper or better termination.
    For a damper I'd recommend:
    For a better termination that seals well:

    If you are using a heat pump dryer you don't need an exhaust fan in the laundry, and as long as your range hood is under 400 cfm you don't need make-up air in the kitchen.

    That being said, your code may require balanced mechanical ventilation for the whole house, and even if it doesn't it's a good idea.

    1. AC200 | | #7

      Thanks for the info on the Cape dampers. They look really interesting for bath exhaust fan ducts. Not so much for dryer vents where cleaning would damage them or kitchen hood with the grease. They say to change them annually for kitchen exhausts but who would realistically do that?

  3. anonymoususer | | #4

    Thank you, Malcolm. Admittedly, I am not sure why the vent termination on our bathroom exhaust fan opens and shuts, opens and shuts, all the time. But we have seen and heard it doing so. It may indeed be due to varying pressures between inside and outside house. It does seem to flap even more frequently on windy days, though. Whatever the cause, we want the problem to stop. We will look into the products you recommend.

    We are aware that range hoods that exhaust < 400 cfm do not need makeup air. What we are trying to figure out is: Does Code require an exhaust fan in the kitchen *in addition to* the ducted range hood?

    It is a relief to know that laundries do not require exhaust fans.

    I dont know whether or not our code requires balanced mechanical whole-house ventilation or not, but we are planning to acquire HRV or ERV because the building scientist we hired told us we will need one or the other (said either is fine in our case).

    1. Expert Member
      MALCOLM TAYLOR | | #5


      No you are fine with just the range hood. I'm not even sure it is required to vent outside under your code.

      On second thoughts - you should probably confirm whether your laundry room needs a fan with your building inspector. Some local jurisdictions do say you need one if there is no operable window, but the right placement of HRV/ERV vents should meet any requirement.

      1. anonymoususer | | #6

        Thank you, Malcolm

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