mounting bath fan in skylight wall?
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  1. #1
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    Oct 2010
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    Question mounting bath fan in skylight wall?

    Need some feedback about installing an exhaust fan in a skylight.

    The large skylight is shared directly above two shower stalls and so I need something that will rapidly take the moisture away from the light well. Our HRV vent that's mounted in the skylight now is not sufficient to rapidly take away the moisture. I can buy a Nutone/Broan humidity sensing fan (QTREN100H) and mount it on the skylight wall but the manufacturer specifically says it's for flat ceiling mounting only.

    As a potential workaround, my questions are:

    a) has anyone here successfully mounted one of those Nutone's in a skylight wall?

    b) would damage occur to the bearings if mounted on vertical axis?

  2. #2
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    May 2008
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    We recently went to a home with an HRV and checked it, however it was completely plugged up and not working. Have you recently serviced yours? If not, I'd suggest looking it over and making sure it's working properly before adding another vent fan. Just a thought.

  3. #3
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    Oct 2010
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    Lightbulb

    Quote Originally Posted by wahoo View Post
    We recently went to a home with an HRV and checked it, however it was completely plugged up and not working. Have you recently serviced yours? If not, I'd suggest looking it over and making sure it's working properly before adding another vent fan. Just a thought.

    To update, I called Nutone and queried them about mounting the exhaust fan model on vertical. They promptly told me that the design of the fan precludes that method and will void the warranty if found to have been mounted in that position. I suspect those big new low sone fans are designed to 'float' in horizontal config only.

    To your point, I regularly service our (Eneready) HRV: clean the foam filters, flush and clean the exchanger, wipe the interior, change the outlet supply pleated filter (allergies), and oil the 2 motors every second year

    Not wanting to screw with Nutone repair warranty issues, etc. I've decided to just continue with using HRV as the primary shower exhaust, and for now drop the idea of installing a separate exhaust fan.

    Background: the original floorplan was originally of 2 separate but back to back rooms -- main bath & ensuite-off-bedroom. We've opened that space up so that the reno'd m.bath tub and reno'd ensuite shower are under the same large 4x4 skylight. They are separated by a 70" tall wall. The original m.bath had its HRV exh vent in the skylight (when it was wholly in the room) and it worked well for the occassional bath. The ensuite had its exh vent in its ceiling. It too work reasonably well for that old shower location.

    What I propose to do now is to reinstall that old ensuite vent also into the skylight, so a total of 2 wall vents there. I suspect that should cover any steam issues trapped in the skylight (which was our biggest concern, hense the separate fan idea), as well as servicing the 2 adjoining bath room-ettes. Makeup supply air is from a vent in the adjacent m.bedroom and vents in other locations in the house. For summer use (PNW), there is the use of a large awning window in the m.bath, and there will be a smaller hopper window within a small exterior glass block wall in the ensuite bath.

    If this HRV rearrangement solves our venting problem then I will need to properly rebalance the HRV system. I don't have a magnehelic guage kit, but in the past I have used the 2 trashbag technique of timing inflation/deflation. And to help with that regulation I've also installed 2 flap dampers at the HRV unit. As well, the supply ceiling vents are screw-in adjustable, and most of the ceiling exhaust vents are adjustable POSH-powered.

    Can you suggest another way that I can more accurately adjust the HRV system?

  4. #4
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    toy could use a remote fan for exhause- intake in wall and fan would be in attic or other convenient area.
    Col 3:23


    questions asked, answers received, ignorance abated

  5. #5
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    Sep 2005
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    Lots of options for fans out there... understand the low sones thingy (nobody wants to listen to a whiny fan).

    I would shop the fan some more... you will find what you want.

    Note: when mounting it... might want to work on the baffle... A backdraft of cold air is not what one wants to greet in the morning shower...
    GA-HVAC-Tech

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  6. #6
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    Quote Originally Posted by ga-hvac-tech View Post
    Lots of options for fans out there... understand the low sones thingy (nobody wants to listen to a whiny fan).

    I would shop the fan some more... you will find what you want.

    Note: when mounting it... might want to work on the baffle... A backdraft of cold air is not what one wants to greet in the morning shower...

    My original intention was to have a separate exhaust fan mounted in the common skylight (replacing the HRV vent ..which would have been moved to another flat ceiling area). One of the stipulations for that fan was with a moisture sensing feature so that when either bathroom wash was used the fan in the common skylight would sense the higher humidity then turn on.

    It still seems logical to me that reverting back to the HRV vent and adding another in the skylight would do the trick. However, it may take a tad longer to evacuate the moisture from the glass vs a dedicated exhaust fan. But the end result may be even more thorough. Plus, the risk of unbalancing the system would be nil.

    Any other thoughts on this is still appreciated

  7. #7
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    Aug 2003
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    How about a skylight that opens? Combine it with a cracked open window that's in the bathroom (if there is one)...in winter, natural stack effect will eliminate the moisture. In summer, the hot steam from the shower may still vent out an open skylight.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  8. #8
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    Oct 2010
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    Quote Originally Posted by Shophound View Post
    How about a skylight that opens? Combine it with a cracked open window that's in the bathroom (if there is one)...in winter, natural stack effect will eliminate the moisture. In summer, the hot steam from the shower may still vent out an open skylight.
    The 4x4 fixed skylight was replaced about 3 years ago with another of the same. So that ain't changing. The residence is a rancher with HRV, so to keep it balanced for Winter use windows can't be opened ..only in the Summer.

  9. #9
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    Aug 2009
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    Beatrice, NE
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    1st question, is the blower on hte H/C equipment tied into the HRV so when the HRV runs the blower runs?

    Can you get a new run from the HRV back to the skylight? What if you tied a duct boaster to the HRV vent to give it a extra CFM when the humidity is a problem, the rest of the time it wouldn't be needed.

  10. #10
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    If you put a vent fan (vented outside) from the bathroom... you will lower the efficiency you paid for by installing the HRV. Think about it... (yeah, even us pro's have to stop and consider things sometimes).

    So it appears there are some compromises to make here... IMO after the compromises are decided on... the action will be simple.

    Let us know what you come up with.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  11. #11
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    Oct 2010
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    Quote Originally Posted by kls-ccc View Post
    1st question, is the blower on hte H/C equipment tied into the HRV so when the HRV runs the blower runs?

    Can you get a new run from the HRV back to the skylight? What if you tied a duct boaster to the HRV vent to give it a extra CFM when the humidity is a problem, the rest of the time it wouldn't be needed.

    The HRV is a dedicated unit with it's on plenum. The rest of the house is baseboard heat.
    The main HRV unit is in the garage with the bathroom about 80' away, so running another separate vent line from the main unit will be too difficult in the attic and through 15" in blown insulation.

    And yes, oddly enough a flyer came to the house advertising a 4" 52db duct booster. I too wonder if putting in that booster in the vent duct leg near the skylight HRV would do the trick. I could connect it to a wall switch (next to the POSH control switch for the HRV) and turn it on when shower is in use.

    Anyone with that experience? Will 52db rating be too loud?

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