Because of the dry climate where we are, I usually don’t make an issue out of this type of plumbing vent run for bathroom fans.
I thought I’d post this recent inspection shot that I did, to see what others think about this?
I believe the perfect solution should be a vent, directly to the exterior.
(And in the imperfect world we live in, it sure looks like this would solve any possible moisture problems,
at least here in low-humidity-colorado.)
Opinions welcome.
I agree vent directly outside however since it’s legal simply venting them to the gable vent without having to cut holes in the roof is the preferred method to save money for builders.
I would be more concerned if it was a dryer vent ,but in a cold climate such as yours , is there not a possibility of freezing up the opening and cutting off attic ventilation.
For new construction around here, the AHJ’s (St. Charles) want the vents 18 inches above the insulation. To a gable, to a soffit, or to the exterior is ok too. We’ve got pretty humid summers, and I’ve not seen much issues with this. The only issues I’ve found is rusted nails from winter condensation/thawing/dripping and that was an older home. Relatively speaking, you almost never see bathrooms vented to the exterior here.
Mark, same thing here, as long as it is 18" above the insulation, it is considered sufficient here.
Steven, is that two bathroom vents and one dryer vent in the smooth duct.?
Makes to much sense to just vent up through the roof with a $5 vent cap?
Hate to see what happens with a prevailing wind, and no ridge vent.
Why is the felt paper directly on the truss framing.?
I know, I know, I ask to many questions right.?:mrgreen:
So you guys in Missouri have no problem with intentionally soaking the underside of roof sheathing that creates mold. ?
We are talking warm ,humid air.
OK.
In that case i guess blocking the Gable vent is fine and dandy.
That’s just it… The humid bathrooms venting to the attic apparently cause no harm. My own home for example has the vent directly into the insulation. There is no ducting at all. Zero, and I say again, zero moisture problem in the attic. Apparently the natural ventilation of the attics around here is sufficient. I’ve only found one older home that had any problems at all, and that was the rusty nails and winter condensation.
Mark you do know that simply because for some reason you never had a problem that it is still a issue?
In the Kansas City Metro it is not a requirement. But I always write it.
Thanks guys, you all are thinking the same as I am.
I did in fact, mention it in my report, but not in an alarming way, but more
of an informational statement.
“Steven, is that two bathroom vents and one dryer vent in the smooth duct.?”
Hi Marcel, I believe its two bathroom vents and one dryer vent.
Makes to much sense to just vent up through the roof with a $5 vent cap?
I hear you, I guess the builders are content with just up into the attic…
"Hate to see what happens with a prevailing wind, and no ridge vent. "
We have some incredibly high winds out here on the front range,
I’ve personally seen gusts as high as 90 - 100 mph, and anything thats not nailed down is blown south…:shock:
Very few homes actually have full ridge vents, more than likely (like this home) the soffit vents and gable vents suffice for breathing the attic.
“Why is the felt paper directly on the truss framing.?”
That is actually the back side of the fiberous type sheathing applied as the skin to this building.
“I know, I know, I ask to many questions right.?:mrgreen:
”
No problem, glad to chat…
Steven, thanks for the reply, and what I meant by prevailing winds, and you just enforsed it with the wind speed you get, won’t this wind just blow in the exhaust ducts and force it in a reverse motion in the house when they are being used?
Just curious. 
You have to keep in mind that most bathroom vents are simply fart fans.
Most exhaust fans have a back-draft damper.
How about the dryer Joe when it is in use with those winds and no flapper at the end of the duct?
I’m with Marcel. Dryer vent should have a backdraft damper (it’s possible there is one at the dryer connection, but not common). Dryer vent should never have a screen (I would consider the louvered gable vent as a screen) to trap lint.
I would make minor mention of the bath vents (SOP requirement in TX). I would definitely call out the dryer vent which will make a big mess and may become obstructed over time.
Definitely called out. But I’m more concerned with insects or birds building nests than with air blowing in.
The back-draft damper for bathroom exhausts is at the fan. But should have one too if it vents outside the home.
Of course, but that’s not the point. The point is, the AHJ doesn’t require it, and anecdotal evidence points to the probability that it isn’t a big concern.
I guess i am asking if you make it a concern or even a mention in your report.
I recently had one(no time to dig pics tonight) where the exhausts were up to the bottom of the roof pots and blocking over 50% of the openings.
At what point would you consider blocking attic ventilation an issue?
