Author Topic: Bathroom ceiling fan venting question  (Read 1682 times)

secondcor521

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Bathroom ceiling fan venting question
« on: September 20, 2017, 03:40:53 PM »
I thought I had an old thread on this but I couldn't find it.  Oh well.

Long story short, my master bath ceiling fan is not adequately venting.  The builder strongly suspects that there is a wasp's nest in the vent pipe.  I tend to agree with him, since he obviously knows more about houses than I do.

The question now is how to fix it.

I crawled up into the attic space today and found the vent pipe.  It is some sort of soft flexible grey material; I would compare it to the material they use for HVAC runs in attics around here.  It is about 4"-5" in diameter.  There are two approximately 90-degree kinks in the pipe, and the total run length is maybe 6 to 7 feet between the fan in the bathroom and the roof vent.  The pipe is attached to the exterior vent with what looks to be a large white zip tie.

I figure I have a couple of options:

1.  (Builder's suggestion) Shove a garden hose from inside the bathroom up through the ceiling fan exhaust port to dislodge and fragment the wasp's nest.  I could try this but am concerned about perforating the side of the pipe.  Advantage is that it is a relatively easy thing to try.

2.  (My best idea if I want to be cheap) Crawl back up into the attic with a pair of scissors or utility knife, cut the zip tie, remove the pipe from the exterior vent, clean it out from that end, then reattach with either (a) another zip tie, or (b) strapping tape that I already have on hand.

3.  (My best idea if I don't want to be cheap) Call the builder and have him help me find someone to come in and do similar to #2.  Advantage is this person could maybe also assess if the 90-degree bends are causing a problem (the house has always had this problem) and would maybe know what to do about that.  Disadvantage is this person might not be careful and could hurt themselves or put a foot through my ceiling drywall, and it's not his house so he may not do a good job fixing it.

4.  Other?

Advice?

Sojourner

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Re: Bathroom ceiling fan venting question
« Reply #1 on: September 20, 2017, 05:05:47 PM »
If you opt to disconnect the vent duct, what's your plan for the wasps in case they're in there?  If they start flying around inside your attic, it will be difficult to avoid being stung since you won't be very mobile in the confined space.

Can you disconnect the duct from both ends and inspect that it's clear?

There is an expanding foam wasp spray you can buy from Home Depot that will encapsulate the wasps and their nest in case you need it, but it will probably goop up your duct/vent.  Bee suit?

secondcor521

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Re: Bathroom ceiling fan venting question
« Reply #2 on: September 20, 2017, 06:35:38 PM »
Good question.  My thoughts so far:

1.  The builder and I think the wasps' nest is probably defunct.  They've moved on to my eaves hopefully.

2.  I climbed up on the roof and sprayed wasp killer into the outside vent.  Maybe that killed some more.

3.  I was going to manually crush the nest from inside the attic by squeezing the vent pipe.

4.  I was also going to bring up the wasp killer spray in the attic and spray it in ASAP after disconnecting the vent pipe from the external vent.

I can't really get to the lower end of the vent pipe.  It's buried under all the ceiling insulation.

Sojourner

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Re: Bathroom ceiling fan venting question
« Reply #3 on: September 20, 2017, 07:30:29 PM »
Not being there to see it myself...

You seem convinced you cannot access the lower end of the duct pipe due to insulation obstruction.  Seems that insulation material would be rather easy to move aside temporarily while you disconnect the pipe. 

If you crush the pipe, you will have to replace at least a portion of it anyway, so why not cut the pipe off at a convenient spot (if you absolutely cannot disconnect it at the lower end) and clean it of any obstructions, then recouple it back on or replace it altogether.  That type of pipe is what, $15 for six feet or so.

Also, if you disconnect the pipe, test the fan before going through all the trouble of reconnecting the pipe.  Maybe the problem lies in the fan unit itself?

ejacobson

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Re: Bathroom ceiling fan venting question
« Reply #4 on: September 20, 2017, 07:47:11 PM »
I am not an HVAC expert but it seems there could be water/mold/dust accumulating in those 90 degree bends. Ideally it would be a smooth duct with as short of a run as possible. The fan itself could be a problem either from some fault or from being underpowered. If it was like that from the beginning, you could check that the model is appropriate for the size of the bathroom. I would start with the fan and work my way up.

FIRE_fighter

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Re: Bathroom ceiling fan venting question
« Reply #5 on: September 20, 2017, 07:54:32 PM »
Just compress the flex duct and see if you can feel an obstruction. I would suggest removing the entire run of flex duct either way. The humidity being removed from your bathroom should really have smooth duct pipe for ventilation. That flex duct has all those rigids where moisture can get trapped. The fan will perform better with the smooth duct pipe installed. It is easy to work with and can be connected with Nashua HVAC tape (not to be confused with duct tape)

AccidentalMiser

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Re: Bathroom ceiling fan venting question
« Reply #6 on: September 20, 2017, 08:18:59 PM »
Just compress the flex duct and see if you can feel an obstruction. I would suggest removing the entire run of flex duct either way. The humidity being removed from your bathroom should really have smooth duct pipe for ventilation. That flex duct has all those rigids where moisture can get trapped. The fan will perform better with the smooth duct pipe installed. It is easy to work with and can be connected with Nashua HVAC tape (not to be confused with duct tape)

This.  Flexible duct has no place in this application.  I would recommend 4 inch metal ducting or thin wall pvc.  I doubt a garden hose is rigid enough to clear a severe clog.  I'd wonder about a builder who recommended something like that.

secondcor521

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Re: Bathroom ceiling fan venting question
« Reply #7 on: September 20, 2017, 09:36:58 PM »
Here's a couple of pictures of what I think they used:

http://www.homedepot.com/p/Master-Flow-6-in-x-25-ft-Insulated-Flexible-Duct-R6-Silver-Jacket-F6IFD6X300/100396935

http://yymultimega.com/product/hvac-insulated-flexible-duct/

...

@Sojourner, I'm not sure why I wrote that I can't access the lower end.  I think it was a functional fixedness moment where I was focused on the wasp's nest that I assume is located closer to the roof end and thus where my problem lies.  Yes, I could move away the insulation - it is just that blown in insulation stuff that looks sort of like white cotton candy and is really light and fluffy.  If you look at the pictures above, the ductwork is kinda crunchy, so I can crush it with my hands and it sort of springs back.  Cutting the ductwork in the middle is a good idea I hadn't thought of and that might work.  Thanks!

As for those of you wondering about the fan...good questions, but I already checked that part out.  The fan blades are spinning, the fan size is the proper rating for the size of bathroom.

Can anyone point me to some smooth ducting options that I could pick up at a Lowe's or someplace like that?  The fan exhaust diameter is about 3" and the roof vent opening looks more like 5".  I will still have to make some sort of joints or bends as the exhaust points horizontally away from the roof vent which is on about a 30-degree angle.

Kroaler

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Re: Bathroom ceiling fan venting question
« Reply #8 on: September 21, 2017, 03:57:47 PM »
Flexible duct material has been used on the last 4 bathroom vents ive seen.

Go to the aisle where they sell bathroom fans.  Should find plenty of replacement options.

yachi

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Re: Bathroom ceiling fan venting question
« Reply #9 on: September 21, 2017, 06:39:43 PM »
If the flexible duct is horizontal (or worse, if it has a belly in it) it can collect water from the moisture in your bathroom air.  I've heard of gallons being found in it before.

AnotherFI_IT_Guy

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Re: Bathroom ceiling fan venting question
« Reply #10 on: September 22, 2017, 07:36:03 PM »
Most bathroom fans have a damper on the side where it feeds air into the ducts.  When they are shipped those dampers are usually taped closed.  Sometimes when they are installed, the workers forget to remove the tape.

I'd suspect that more than a wasps nest since you said it has always been like this.

But, this is not easy to check without removing the duct in the attic from the fan body.

One more thing to look for next time you are up there.

Good luck.

secondcor521

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Re: Bathroom ceiling fan venting question
« Reply #11 on: September 22, 2017, 10:00:37 PM »
Thanks everyone.  I'll check out those things when I go up there next.

I think my plan will be to turn on or remove the fan, climb up in the attic again, cut the cable tie from the upper end of the ducting, remove it from the roof vent, straighten out the ducting, clean out the existing ducting with some sort of rod, then reattach it to the roof with more cable ties.  Possibly try to make the bends smoother if I can figure out a way to do that.