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Community and Q&A

Bath fans

raul4817 | Posted in General Questions on

I am planning on exhausting 3 baths all on the same floor with one exhaust fan. I have found some nice panasonic inline fans but I have also seen some multi port exhaust fans with similar cfm made by fantech, broan, etc. Any insight on which way to go here. Is one prefer over the other.  Cost is similar and install seems fairly similar. They will unfortunately exhaust all baths even if all 3 are not in use but this is my prefered method and typically 2 will be in use simultaneously.    

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  1. Expert Member
    Akos | | #1

    I've lived with a couple of these over the years. My biggest beef with the setup is they tend to be noisy. The sound rating doesn't tell the whole story as most also tend to hum which carries in the structure which gets annoying. Try to mount the unit a bit away from bedrooms.

    The setup does work reasonably well. Best for control is motion activated switch in each bathroom in parallel to the fan. You can also go with 4 way switches, but then you are always trying to figure out which way is on.

    If you can find one with an ECM blower, it will be much better than any capacitor motor regardless of sound specs.

  2. Expert Member
    Peter Engle | | #2

    I've seen this setup with all of those models. I disagree with Akos that they hum. I've seen some that are so quite that you can't tell they're running but they are still moving quite a bit of air. Granted, with those the fan was mounted at some distance from the bathroom. Panasonic seem to be making the quietest fans these days, with Fantech coming in a close second. I find that Broan fans are the cheapest but also the loudest. If you can mount the fan with a "soft" mount, that helps any transmitted noise. A simple sheet of rubber between the fan and the structure is often enough.

    I use this setup in my VT house, and the fans serve two bathrooms and a shower room. Each has a timer switch installed. You hit the button for how long you want the fan to run and it does. This prevents forgetting to turn it off. It is quiet enough that this was a concern.

  3. raul4817 | | #3

    Thank you both for the quick replies. I'm not super hung up on the noise issue, It will be located somewhere between the 3 baths and that most likely will be above the laundry room. Ideally I'd like to go with a timer switch but the motion could be a nice fail safe with a 7&10 year old that are very forgetful. I would like to stay away from broan since i've had a negative experience with a smaller unit for my 1st floor bath, I currently have a delta breez with a DC motor that I really like. Im looking at fantech multi port or panasonic inline. Just unsure if there is an advantage to running dedicated ducts to a multi port vs wyes and tees to an inline.

  4. raul4817 | | #4

    So Ive narrowed down my exhaust fan to a fantech FG6M EC 363cfm with speed control.

    I am however playing with the idea of getting the bigger fanctech FG 6XL 483cfm. The main reason for upgrading to the larger size was to possible have an intake located over my centrally located staircase foyer. The idea was to have this duct run with a damper that could be opened up during the shoulder seasons to bring some breeze in through open windows. not sure if this would be worth the extra cost and labor in sheet metal, Could the 3 exhausts in the baths be enough if i dialed up the fan speed.

    would I be better served adding this register in the conditioned attic to remove some air periodically?


  5. Expert Member
    BILL WICHERS | | #5

    You could do that, but it probably won’t get used much.

    BTW, it’s not hard to damp the vibration of the fan so that the sound doesn’t conduct into the structure and get annoying. Here is a simple way to do it, based on the way large pumps (and other vibrating things) are isolated from the structure in multistory commercial buildings to keep sound levels down:

    Get a precast concrete paver of sufficient size for the fan. This probably means 18x24 inches or so. It’s going to be heavy, but that’s the point: you want the mass of it. Build a simple platform for the paver with some plywood or 2x framing lumber, whatever is handy.

    Get some SPRING TYPE vibration isolators. McMaster Carr is one source. Note that these are rated for specific weight ranges since they work best when the spring is PARTIALLY compressed. Take the weight of your platform, precast paver, and fan, divide that by four and that’s the weight you’ll be applying to each vibration isolator. Try to find a vibration isolator that will be operating in the approximate center of its allowable range when supporting whatever your assembly weighs. If your platform+paver+fan weigh 77 pounds, that’s 19.25 pounds per isolation mount (you use one in each corner). Maybe you can find a vibration isolator rated “16 to 25 pounds”, perfect!

    Mount the fan to the paver using some tap cons, plastic anchors, whatever is handy. Mount the paver to your wood platform the same way. Mount a vibration isolator to each corner of your platform and bolt the vibration isolators to the structure of the house.

    Make all connections to the fan with flex duct (for vibration isolation, you need a short piece on either end of the fan, the rest of the run can be rigid ducting). Use flexible cable for the power too, I like SJE. If your local inspector doesn’t like that, use a piece of MC cable but make sure it has stranded conductors and not solid.

    The mass of the paver dampens the vibration of the fan assembly. The wood frame provides a bit more mass and an easy way to get the vibration isolators mounted in positions that will line up with your house framing. The vibration isolators decouple the paver/fan assembly from the structure to limit any transmission of vibrations (sound) to the structure.

    An assembly like this will make the fan FAR less noticeable. Try to use spring type vibration isolators here, they work best. If you can’t find those, use the rubber kind. Don’t use cork pads, they don’t work well in this application.


  6. justinlacy | | #6

    raul4817... what did you end up doing, and how is it working for you? I have a very similar situation on a new build. Any reason why you went with something like the FG6M instead of one of Fantech's multi-port fans, like the CSV300A that has four intake ports and one exhaust port? Did you put together your own Y's to connect the ducts from the different locations? What did you do for controls in each bathroom?


    1. Expert Member
      MALCOLM TAYLOR | | #7

      I don't understand the thinking behind this setup unless you are using the bathroom fans as part of y0ur whole house ventilation strategy.

      You run bathroom fans to remove either moisture or odours. Why exhaust air from rooms where neither is present because one of the others requires it?

    2. raul4817 | | #10


      I went with a an inline fan since I needed to exhaust 3 baths and most multi port fans are designed with either 2 or 4 ports.

      In my situation 2 of the 3 showers are used simultaneously daily so my penalty on exhausting the 3rd bath is minimal. I also installed dampers inline but have yet to adjust them to dial in the cfm for each bath.

      With the weather breaking I will open windows and use the fan throughout the day just to bring some fresh air in
      ( depending on outside humidity level).

      But as malcolm stated this is indeed going to be part of my whole house ventilation strategy. I will at some point park an ERV in the basment and exhaust from the 1st floor bath and basement bath via the erv. These bath will rarely be used for showering if ever.

      I have one penetration and more than adequate moisture removal even with both showers going and probably even with the 3rd going. I did oversize it a bit but installed a potentiometer (fantech I believe) I still need to adjust everything just have been swamped lately.

      Hope this helps
      I will try to upload a few photos soon


  7. justinlacy | | #8

    I'm trying to reduce the number of exterior wall penetrations in my unvented attic. I think reducing three 4" diameter holes to one 6" diameter hole is generally a good thing (and subjectively, it looks better). However, the point you bring up is the same thing I was wondering about. That's why I asked "...and how is it working for you?".

    1. Expert Member
      MALCOLM TAYLOR | | #9

      I do see the appeal. It's too bad there isn't some simple way to control which bathroom the air is being drawn from. All the solutions I can think of are either too complex or prone to failure.

      Funny they seem to be able to easily do it in vehicles. The one switch moves air to all sorts of different locations and combinations.

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