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Thread: New bathroom reno fan leaking

  1. #1
    DIY Member farmboy101's Avatar
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    Default New bathroom reno fan leaking

    Hi All....I am perplexed.....

    Just did a complete reno adding a top of the line shower, body sprays, rain shower head etc etc. The size of the bathroom is approx 40 sqft and half of the space is the shower. So we figured that we should upgrade the fan and we installed a NuTone 110 CFM as we thought the increase in the steam from shower upgrades would be necessary. Totally love the shower but we are finding that before the end of the shower the fan is dripping water quite alot!....So thought ok we need to double check everything so we installed insulation all around the metal fan housing thinking the metal was cold and the steam was condensating rather instantly. We also covered this glued on insulation with a vapour barrier plastic 'hood' (sorry not sure what they are called) More commonly used on electrical boxes. Tuct taped all the joints to make sure we have a good seal. Then removed the metal ducting and replaced it with the insulated ducting pipe, double checked the flapper valve (works fine) and vented it as it was, out the soffit where there is a proper vent for the fan. Now we also thought we would add an extra some bats of insulation on top of all this along with all the newly blown in insulation.
    My question is does anyone think the fan is too big for the size of the room?? At a loss...after doing all the redo on the venting we were so discouraged that we still have the same issue....
    Please help these poor discouraged DIY ers. WE have resorted now to not using the fan and just open the window, but know this is not the solution.....Also FYI we took out the old fan which was a 50 CFM....which we never had a problem with it dripping...????? Please help.....
    thanks very much, fb

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    I think the problem is not the fan, but the significantly higher humidity in the shower from all of the new sprays. You may need to check the slope of the vent so that it can drain to the outside rather than back into the room. A smooth vent and minimum turns will help move the air at it's max, and hopefully keep the dewpoint further away (ideally, when it hits the outside), but if the slope is back into the room, it will drain there regardless.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member farmboy101's Avatar
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    Thank-you for your input....at first this was one of our thoughts but the line does have a nice slope towards the soffit vent....

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    One who lurks Basement_Lurker's Avatar
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    It sounds like you have done everything properly, and no, you can't oversize the fan, nor is the fan that you have installed over sized for your application. I am curious as to the venting run that you have...what size venting did you use, how long is it, and how is it routed? Taking a total stab in the dark, I tend to think that you have a good sized run in an freezing cold attic, and that your fan output is compromised somehow.
    Broken promises don't upset me. I just think, why did they believe me? -Jack Handy


    www.blackbirdkitchenandbath.com

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Humid air will condense when it cools, and that condensation is going to flow downhill until it finds a spot to drip out.

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    Plumber jimbo's Avatar
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    To me, the term 'soffit' means something under the eaves. IF that is where you vented it, that is a no-no. You will rot the wood out there. It is not the cause of the condensation, however. Did you use a smooth wall vent pipe, or corrugated? Check at the soffit vent outlet for good air flow.

    Normally, 110 cfm is PLENTY for 40 square feet, but it sounds like you use the shower as a "steamer" even if you do not have an ACTUAL steamer. The next step up from what you have would be an inline duct fan installed in the attic.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The soffit is not my preferred exit location. If you don't have a true vent hood there and are relying on the holes in it, you are probably creating too much backpressure and not getting the flow the fan is capable of, slowing it down, allowing more moisture to condense. It needs essentially an open hole when it is running to work properly, with no grill or slats to try to push through.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member farmboy101's Avatar
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    Ok here is a couple more items that you guys have asked about....The pipe we used was recommended by a local house builder and he said this is all he ever uses??? We went to HD and bought the insulated duct piping which comes all wrapped in insulation and imagine stays nice and toasty in its wrap. It is in about a 4' run going down from the fan housing venting into a proper vent hood attached one of the soffit boards. The pipe is a 4" diameter which we thought was the correct size for the fan housing. The pipe is attached to the fan box in the bathroom ceiling and runs parrallel to the ceiling slightly downhill which then exits at the vent outlet. We did a test and the steam was pouring out of the venting so that lead us to believe that we had covered all the bases but shortly thereafter the dripping started???? This morning decided to do another simulation and the during my shower left the fan off and opened the window and left the bathroom door open and after showering looking closely at the fan box in the the ceiling I noticed the condensation on the metal housing . It didn't drip while I was observing it but thinking if I had of turned the fan on the dripping would have started?? Anyways just thought I would try and undo the vent outlet on the soffit side and let it run fully open....If per chance that did solve it how to seal it from cold entering back in???
    anyways guys ...thank you so much for your thoughts and look forward to figuring this out without swearing too much!
    cheers , fb

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    Does the vent hood have a damper? Is there another damper anywhere in the system? Insulated duct has its advantages, but insulating solid duct does, too, since it is smoother and straighter.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member farmboy101's Avatar
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    Hi Jim,

    Yes the vent housing has a damper on unit and the vent in the soffit has a damper that opens while the fan operates and closes while its off as to keep the cold air out.....
    We are a bit perplexed as the old shower produced as much steam and we had a way smaller fan and never seen any sort of condensation like this....just doesn't make sense.....
    thanks for your input!
    fb

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    Bigger fan, removing more hot, humid air, more moisture, more opportunity for it to condense. The old one may have condensed some, but the volume was low enough you didn't notice.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member farmboy101's Avatar
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    that does make sense......thank-you

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    One who lurks Basement_Lurker's Avatar
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    Hmm, I would definitely agree with jadnashua if this were a long run, but 4' is nothing. I am inclined to think something else is going on here, like you have a heck of a lot more steam than you are letting on. A smaller fan wouldn't pull enough air out of the room, and you would just get condensation on the ceiling. My guess still is that there isn't enough airflow to meet your requirements, and you either need to upsize the fan or you will have to change to a wall mount fan since you have access to an exterior wall.
    Broken promises don't upset me. I just think, why did they believe me? -Jack Handy


    www.blackbirdkitchenandbath.com

  14. #14
    DIY Member farmboy101's Avatar
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    We are going to pull off the vent on the end of the pipe off and see what it does wide open....The hot shower produces the same amount of steam with the previous original shower. The body sprays and rain shower head have barely been touched. Really don't think the steam has increased with the reno as the amount of water available is still the same ...ie well water and hot h20 tank is unchanged.....Also the house is really sealed tight and maybe the it is starving for air??
    cheers, fb

  15. #15
    DIY Senior Member jch's Avatar
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    Is the metal fan box itself covered in insulation? Or is it getting cold from exposure to attic air?
    ----------
    - John

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