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A question about bath fans

John Barry | Posted in Green Products and Materials on

We have a steam shower in our master bath that we use a lot this time of year—we live in Chicago and have kids with perpetual colds—and the nearby windows end up with condensation on them more than I would like. We’ve begun to run the bathroom fans a lot in order to mitigate the moisture on the windows, but our fans are relatively inexpensive—and loud—ones from Broan (80 cfm/2.5 sones) that were installed by the guy who built our house and I’m beginning to think that it would be worthwhile upgrading to fans that are quieter and more powerful.

However, I’m wondering if the current set-up is ideal. The bathroom is really three separate rooms—a large main area (14x7x9), a walk-in shower (8x4x9), and a water closet w/ toilet (5x5x9). The existing set-up has one Broan in the main area near the shower and the other in the water closet. Intuitively—I have no relevant expertise—this does not make sense to me; I would think that you’d want a more powerful fan in the main area (to deal with general moisture issues in the bathroom and to deal with the shower) and a less powerful one in the water closet.

My sense in terms of flow is that for the entire bathroom—155 sq. ft./1,395 cu. ft.—we should have ~200 cfm (186 cfm, to be more precise), ~150 cfm in the main area and ~50 in the water closet. Does this make sense?

Also, any advice on particular products—Panasonic v. Broan? Anyone have any experience with Delta, Stelpro, or Aero Pure fans? Thanks much.

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  1. Doug McEvers | | #1

    The Delta fans are quiet and solidly built, DC motors too.

  2. Dan Kolbert | | #2

    We've used Delta's as well, and been very happy with them.

  3. John Klingel | | #3

    I installed a Panasonic Whisper Quiet (something like that) that was recommended here and it is a thing of beauty. Very quiet, good cfm, and a programmable high setting.

  4. GBA Editor
    Martin Holladay | | #4

    Almost everyone agrees that Panasonic has perfected the bathroom exhaust fan, so you should go out and buy yourself a couple of Panasonic WhisperComfort fans.
    I don't know how many minutes per day you are operating your fans, but it makes sense to increase the run time until the condensation disappears from the windows. You may not need more powerful fans -- just longer run times.
    Powerful exhaust fans have disadvantages; especially when combined with other exhaust appliances (clothes dryers, range hood fans, power-vented water heaters), they can contribute to backdrafting problems (pulling air backwards down your chimneys).  That's why I'd rather see small fans running for many minutes or hours, rather than a powerful fan running for a short time.

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