Venting bathroom fan into attic


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Old 05-14-15, 10:01 AM
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Venting bathroom fan into attic

Just replaced my master bathroom exhaust fan, and discovered that the old fan was simply connected to a short 3 or 4 foot run of Duravent-type flexible ductwork venting into the attic. The builder held the end of the duct up above the insulation with a harness screwed into the plywood roof deck.

This is within about 5 feet of a soffit vent, and I see no evidence of mold or moisture damage. I went ahead and just connected the new fan to the same duct for now.

My question is, I know it isn't recommended to vent into the attic - but is this a code violation? The house was built in the mid-90s but I just bought it last year. I'm surprised my home inspector didn't see it.

House is in Kansas.
 
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Old 05-14-15, 10:19 AM
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Unless you hired an independent home inspector with no connections to the real estate agencies involved, don't be surprised at anything you find that should have been mentioned. But that's another topic.
If and how much mold grows is directly related to how often and how long people run that fan. if the previous owners never used it, then mold would not be a problem.

Codes vary and enforcement varies along with it. But "best practices" would say to vent it to the outside. In order of preference, through a gable end wall, through the roof, and last out that nearby soffit. Venting out a soffit (and not jut pointing the duct at the soffit) doesn't work real well when air is flowing into those soffits to ventilate the attic. Some will advise blocking the soffit vents a couple of feet to either side and there are specific vents for soffits that perhaps direct that air flow further away.

Others here may have more on the code issue.

As an added note, insulation, air sealing and ventilation, including where that duct goes are all becoming hot topics for new home buyers. So, now or when you sell it should be fixed.

Bud
 
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Old 05-14-15, 10:54 AM
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I think I've got a gable end wall close by that would avoid punching another hole in the roof, but I'm leary of cutting any holes in my house. Not sure if that's within my capability to do it right or not.
 
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Old 05-14-15, 11:18 AM
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Welp, never mind. No gable wall at that corner of the house. So I guess I'll punch a hole in the soffit for a round 4" soffit vent. They make round soffit vents specifically for venting exhaust fans, so I assume they're adequate for the job?
 
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Old 05-14-15, 12:29 PM
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This is what can happen when venting out the soffit.
https://www.google.com/search?q=soff...2F%3B300%3B225
Far better to go out the roof.
With proper roof venting the hot moist air just gets suck back into the attic if you run it out the soffit.
 
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Old 05-14-15, 12:30 PM
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I've never put one in a soffit, but a through the wall vent usually has a gravity close shutter that would not work in a horizontal position. Something like this where it is attempting to blow the air away from the soffit.

Bud
 
 

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