Stopped by a house to pick up a radon test; I’ll be inspecting the house this coming Tuesday. Built in 2017, 7,300sq ft, 6/8. Looked up on the roof and saw what looked like an AAV on a plumbing vent pipe. Is this right? I’ve tried researching AAV on external vent but come up empty. I was just wondering if anyone else has seen this, and if so, is there anything out of the ordinary I should keep an eye out for in the inspection. Thanks for the feedback!
New one on me. My WAG is an attempt at critter control. 
My WAG is that they were getting whiffs of sewer in the yard, and this was a fix. Wouldn’t work in my area during winter. A better solution would be to extend the pipe higher.
Or in a window to the left of it.
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Another issue worth exploring, these shingles don’t look right. Possibly installed too tight in cold weather, or maybe something else.
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For proper operation (pressure balancing), at least 1 outdoor vent needs ability to breathe in and out. Even if it was rated for outdoor use, it would still be wrong because it only lets air in.
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I’ve never seen an AAV installed on an external vent like this. I would call it out as the AAV was installed in a location that it wasn’t designed or intended for.
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Often with priviate sewage systems(septic tanks) you will get wiffis of sewer gas from the vent closest to the septic tank. They do make filters for this and you can find dozens of brands, shapes and colors. Another option is to install an AAV like you see in the picture.
If that is not on a septic system and as long as there is another DWV on the system going to atmosphere that single vent with the AAV is not hurting anything. In my report, I will also tell my client to get with the owner for more information on why the AAV was installed like that.
I concur.
Likely several issues combined.
1: Poor siding roof deck clearance.
2: Poor composition shingle to sidewall clearance, causing expansion & contraction.
Clearance: A minimum gap of 1/2" inch to 1" inch between the bottom of the siding and the top of the roof shingles is called for.
3: The metal sidewall step flashing, underneath the composition shingles and abut sidewall, was not installed correctly, snug fitting the deck and side wall, and secured to the deck or sidewall so that the roof deck and side wall can move independently. If not secured/fastened properly the flashing will cause the composition shingles to twist and lift.
Yep. I often see these lifted from the step flashing.
I’m confused. It’s already been noted as wrong and Robert confirmed it with supporting information. What is the new photo supposed to show that the first one didn’t?
Yeah, you’re right. I did say I was going back today so I thought I’d follow up with my findings. But, like you said, it’s already been noted as incorrect.