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Community and Q&A

Continuous exhaust bathroom fan

FrankFulton | Posted in General Questions on

Results of our recent energy audit stated that we need to increase ventilation in our 1952 Cape (2600ft downstairs, 900ft upstairs). The recommended solution was to install a continuous bathroom fan in the centrally located bathroom on second floor. BR has window but no fan.

I’ve read several related articles here on GBA regarding ventilation and bathroom exhaust fans in particular.

Given our 1952 moderately loose house (currently 7330 cfm – we are tightening), is there any reason not to “keep it simple” and just install Martin’s recommended 80cfm Panasonic Whisper Green fan, in the 2nd floor bathroom? Or, given our square footage and layout (long first floor), should we consider another approach to ventilation?

Also, is it better to vent through the attic and out the gable wall, or simply out the bathroom wall?

Thank you.

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  1. Expert Member
    Malcolm Taylor | | #1


    Out of curiosity, what was the reason they gave for increasing ventilation? Was it due to high levels of humidity, based on the recommended rates for the size of the house, or...?

  2. FrankFulton | | #2

    TBD - I've requested this info. I suspect general air quality, but the house is leaky so I'm not certain.

    For sure, there is too much humidity - eg, on first floow an internal fountain that we are trying to drain (but keeps dripping!). In basement, there had been a mini-flood, and I found some soggy drywall w mold hidden inside the paper up to 12" of the floor, but <10 see.

  3. GBA Editor
    Martin Holladay | | #3

    You won't regret installing a Panasonic exhaust fan. Exhausting out the bathroom wall is one option that works.

    I'm a great believer in common sense. It's your house -- so you get to operate the exhaust fan any way you want. You might want to put it on a 24-hour timer. There is no reason to run the fan for 24 hours per day if you don't want to.

  4. FrankFulton | | #4

    Will this fan “go a long way” toward solving our ventilation issue (whatever it is)?
    Thank you

  5. GBA Editor
    Martin Holladay | | #5

    A bathroom exhaust fan can meet the ventilation requirements set by ASHRAE 62.2 (the established standard for residential ventilation), as long as the fan is properly sized and commissioned. More information here: Designing a Good Ventilation System.

    But your reference to a "ventilation issue" is confusing. If you can't articulate it, we can't help you address it.

  6. Reid Baldwin | | #6

    Consider a switch like that described at:
    It runs the fan:
    - whenever the bathroom light is on,
    - a programmable amount of time after the light is turned off, and
    - a programmable minimum number of minutes per hour.
    The runtime associated with the bathroom light takes care of moisture associated with showering. The minimum time per hour takes care of whole house ventilation. If your ventilation needs change due to future air sealing work, you can reprogram the runtime.

  7. Rob Myers | | #7

    I have 2 Whisper Green fans installed in a new off-grid build. If you buy the type with the sensor, they will run at a low background speed (I seem to recall the minimum is 40 cfm), the speed automatically changes to a selected value up to 80 cfm when the room is occupied and the fan stays on at the higher speed for a programmed amount of time after exit. They draw very little power and at low speed you really can't hear them (although I do have to point out that my hearing has not exactly improved with age).

  8. FrankFulton | | #8

    Thank you Martin, Reid, and Rob.

    The energy auditor explained that he included the fan simply to ventilate the upstairs bathroom, which is currently unvented (but does have a window).

    We will add a fan to address moisture in this bathroom (although the house has had no fan for 70 years!), but I'll wait until after air sealing and insulation are complete to decide on a fan size, and switch.

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