# Is this an acceptable way to vent bath fan out gable vent?



## Marky82 (Dec 17, 2015)

My parents have a raised ranch. Last year they had their master bathroom renovated and part of that was installing a new Panasonic WhisperCeiling fan/light/heater. Last night, out of curiosity, I went up in their attic since my Dad hasn't been up there since I was a child (I'm now 34, lol). I noticed someone installed the new bathroom fan using flexible ducting. The flex duct runs about 15 feet over the rafters then goes sharply upward and is tied to a 2x4 brace using extra pieces of 14 gauge NM. The end of the duct points towards the gable vent but it's about 2 feet away from it.

Is this even allowed by code? I thought bath fans need to exhaust to the outside? 

What is the best way to fix this? I know best practice is to use rigid ducts with the shortest run. In this case they could either go out the roof or keep the long run, switch to rigid ducting wrapped with insulation, and install a dedicated vent lower in the gable wall. I didn't mention eves because they have soffit vents and running it out those would cause some of the humid air to come back in.

Here are pictures. Sorry for the poor quality but there wasn't much light and I had to use the zoom on my phone.

*This is the bath fan. You can see part of the flex duct is crushed... almost seems like someone stepped on it. *









*This is the end of the duct pointing towards the gable vent. You can also see the large bee/wasp nests at the top and bottom of the vent (yuck!).*


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## beenthere (Oct 11, 2008)

That is not proper. it is suppose to be terminated with its own vent flange/hood. 

Also, that pipe is crimped, so its not venting properly.


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## Windows on Wash (Aug 30, 2011)

+1.

Not ideal, but far from the worst I have seen. 

Needs to go through the gable end wall and it should be run along the bottom of the trusses and insulated over the top of it.


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## akjose (Jan 1, 2013)

Wouldn't it make more sense to just turn the fan 180 degrees and vent out the soffit. 


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## beenthere (Oct 11, 2008)

akjose said:


> Wouldn't it make more sense to just turn the fan 180 degrees and vent out the soffit.
> 
> 
> Sent from my iPhone using Tapatalk


Venting out the soffit, lets the humidity back in the attic, where it could condense.


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## joecaption (Nov 30, 2011)

I would have vented it right out the roof that only a few ft. away to avoid the long run to the gable.


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## SeniorSitizen (Sep 10, 2012)

Disable the fan October - May, that's when you usually need all the moisture you can get within the structure. At times when toilet odors may be objectionable, Glade has provided a solution with Cinnamon and Roses to mask those odors that usually dissipate on their own as fresh air seeps into the house cracks and crannies.

Enable the fan June - September when we normally want the air just a tad dryer.

It's just one of those bi-annual events along with all the other winterizing and summerizing of our properties.


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## akjose (Jan 1, 2013)

beenthere said:


> Venting out the soffit, lets the humidity back in the attic, where it could condense.


Not tracking on what you are saying. I mean to actually have a vent through the soffit to vent the humidity out. not just hanging there. Such as this one: http://www.hvacquick.com/products/r...oWfEjOWsaYUZp4OOlrjd9ql-Ykp0QFDxNBhoCq8Hw_wcB

If done correctly it would be better than trying shoot it out the gable or trying to poke a hole in the roof which could lead to more problems down the road.


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## Marky82 (Dec 17, 2015)

Thanks for the responses everyone. Right now I'm thinking I'll install a vent lower in the gable wall and run rigid duct wrapped with insulation from the fan to the exhaust vent. I'll have to find out the fan's model number and see the recommended maximum distance. If it's close I'd rather go through the gable wall than the roof.



akjose said:


> Not tracking on what you are saying. I mean to actually have a vent through the soffit to vent the humidity out. not just hanging there. Such as this one: http://www.hvacquick.com/products/r...oWfEjOWsaYUZp4OOlrjd9ql-Ykp0QFDxNBhoCq8Hw_wcB
> 
> If done correctly it would be better than trying shoot it out the gable or trying to poke a hole in the roof which could lead to more problems down the road.


This would still allow some moisture to reenter the attic. Soffit vents are intake vents, drawing the outside air in, so even though you're blowing the moist air on the outside of the soffit it's so close that some will be sucked back in.


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## akjose (Jan 1, 2013)

Marky82 said:


> Thanks for the responses everyone. Right now I'm thinking I'll install a vent lower in the gable wall and run rigid duct wrapped with insulation from the fan to the exhaust vent. I'll have to find out the fan's model number and see the recommended maximum distance. If it's close I'd rather go through the gable wall than the roof.
> 
> This would still allow some moisture to reenter the attic. Soffit vents are intake vents, drawing the outside air in, so even though you're blowing the moist air on the outside of the soffit it's so close that some will be sucked back in.


I see, IMO that is negligible. Still though, you could turn the fan 180 and exit through wall for a short run. It _should_ be below soffit, but that may still be too much moisture for you.

Somethings to keep in mind: My bath fan exits over my head in my bedroom with a 3 louver exit on the wall...it is on the weather side and it has been flapping like crazy lately, if were run on the short distance to other exterior wall it would be not flap nearly as much, i wouldnt hear it at all cause the duct wouldnt be over my head and the fan wouldnt have to push as hard. Also, I don't think it necessarily has to be rigid duct as long flex duct is properly stretched. I have seen lots of flex ducts carry the moisture just fine with no problems.


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## beenthere (Oct 11, 2008)

akjose said:


> Not tracking on what you are saying. I mean to actually have a vent through the soffit to vent the humidity out. not just hanging there. Such as this one: http://www.hvacquick.com/products/r...oWfEjOWsaYUZp4OOlrjd9ql-Ykp0QFDxNBhoCq8Hw_wcB
> 
> If done correctly it would be better than trying shoot it out the gable or trying to poke a hole in the roof which could lead to more problems down the road.


Bathroom vent hood for soffits aren't allowed by code in many areas. As they allow moisture to come back in the soffit, and condense in the attic.


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## PoleCat (Sep 2, 2009)

How do we even know if there IS a soffit? Some gabled roofs have no soffit whatsoever. 

Gable vents are typically exhaust but a small breeze changes this. I would run the pipe so it exits at the base of the gable as far from the vent as possible. Use a gradual drop so heavy condensation can run out. A hot shower on a winter morning will generate enough moisture in the pipe to run back into your fan otherwise.


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## Gary in WA (Mar 11, 2009)

From your thread first post; "I didn't mention eves because they have soffit vents and running it out those would cause some of the humid air to come back in."--- good for you!

IMO, run some smooth wall out a ways, enough to add a 45* to get over the cj's, then another where needed to sit slightly higher than the termination hood- to allow condensate to drain to exterior. Though there shouldn't be much with the metal pipe encased in 4 or 6" HVAC flex duct, complete with vapor barrier plastic. Flex for piping has 2+ times as much area (than smooth pipe) for trapping wet air, coating the inside with moisture. Hence the recommendation to go one size larger for rated airflow due to turbulence created- without proper support, fully stretched or kinks/sharp bends; https://www.thefreelibrary.com/Pres...n-metallic+flexible+ducts+with...-a0201591046
Terminate at least 3' from window openings or other house opening.

Gary


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## user_12345a (Nov 23, 2014)

You can use pre-insulated flex. flex is fine if the pipe is sized large enough.

the type of pipe used in your pic is totally unacceptable. it's only good for short runs, as you can see it's easy to damage.


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## Pern (Jan 8, 2017)

Marky82 said:


> My parents have a raised ranch. Last year they had their master bathroom renovated and part of that was installing a new Panasonic WhisperCeiling fan/light/heater. Last night, out of curiosity, I went up in their attic since my Dad hasn't been up there since I was a child (I'm now 34, lol). I noticed someone installed the new bathroom fan using flexible ducting. The flex duct runs about 15 feet over the rafters then goes sharply upward and is tied to a 2x4 brace using extra pieces of 14 gauge NM. The end of the duct points towards the gable vent but it's about 2 feet away from it.
> 
> Is this even allowed by code? I thought bath fans need to exhaust to the outside?
> 
> ...


Not good. Use adapters and 6" insulated R6 or better flex duct. Vent out end wall, gable.


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