Connection between roof vents and bathroom vent fans

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Old 11-29-15, 03:56 PM
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Connection between roof vents and bathroom vent fans

Hello-

I had my roof recently replaced. With my old (original) roof, the builder ran rigid ducting from our bathroom vent fans to vents (not sure what they are called) on our roofline where the warm, moist air exited to the atmosphere.

There was a noticeable amount of water dripping from our master bath vent fan today onto our bathroom floor (never had this before), so I went up into my attic and saw (see picture) that the roofers connected my old original rigid ducting to the new roofline vents with a long length of flexible ducting, which I thought was weird for three reasons. One, they used a really long length of flexible ducting when only several inches would be needed, two, why didn't they just connect the old rigid ducting to the new vents directly, and three, why use this flexible ducting which I assume disrupts the smooth flow of air and would cause water to condense on the inside of the ducting itself?

Further, they left a "p-trap" (like under a sink) with this flexible ducting (see same picture), which I assume does two bad things: traps water in that p-trap and disrupts the smooth flow of warm, moist air out to the atmosphere through the roof vent. It's hard to tell by this small picture, but they basically stood the rigid ducting up, then put the flexible ducting in an "S" shape between the top of the rigid ducting and the roof vent.

Are these new connections with flexible ducting standard practice? It just doesn't look right, and somehow water is flowing down this ducting back through our vent van onto our bathroom floor.

Thanks

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Old 11-29-15, 04:01 PM
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It could have been run horizontally out that gable end that is in the background, so that the duct could be covered with attic insulation. (BTW, where is the insulation?)
 
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Old 11-29-15, 04:29 PM
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My house is a townhouse. The wall in the background is the adjacent unit's wall.

The insulation is "below" me. I live in a ranch style, single floor townhouse. When I took the picture, I had climbed up into the roof "bracing" (not sure what it is called) so that I could get close and get a picture. There is blown insulation below me.

That's the duct. It's not running horizontally.
 
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Old 11-29-15, 04:32 PM
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Vent should have been ran straight out the roof.
 
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Old 11-29-15, 04:38 PM
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Can't say one way is right or wrong, but the trap was put in there to prevent minor condensation from leaking in, and it was a good idea.... just didn't work. Some will use a tee instead, and cap the bottom to hold any condensate until it can evaporate.

Running horizontally like I mentioned is usually preferable. Having it ducted directly to a dedicated vent is usually the best idea. One like this. This is not the same as a roof vent, which is where they ran it. It would be run horizontally to the nearest practical point, probably somewhere low on the roof. Keeping the duct under the insulation helps prevent condensation. In snow prone areas, the hood needs to be kept clear in order to function properly.
 
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Old 11-29-15, 04:48 PM
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The roof is being replaced by insurance, so I can't really tell them that I want to change the venting direction from the roof (the way it was) to horizontal.

Why didn't they just reattach the rigid ducting that was already in place to the new roof vents?
 
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