Really, when it comes to averages or percentages, two out of three isn't bad. Unless it's bathroom vents.
They need to be 100%. They need to not fail. They need to find their way directly outdoors.
During home inspections I like to see where the bathroom vents are blowing.
If I can't see where I ask my client to turn on the fan(s) so I can hear the sound in the attic space.
But for sure actually seeing where they blow out is best.
In this case there are three bathrooms upstairs.
So I should see three vents tubes, and one, two or three exhaust ports going outside.
Such an arrangement as this is common these days, where all combine to blow out a single covered opening outdoors. From the yard outside, if I see the big cover, I know to look for a combined exhaust location in the attic. And I know where to look.
Unfortunately, the fabled and oft-used taped connection is also an oft-poorly-taped connection.
And disconnections are common.
So, in this case, seeing the above I looked for the recalcitrant vent tube.
I finally found the little hoodlum, around the corner, by itself, hanging around the bars, doing nothing good, and blowing in the wind. When the bath fan was turned on, the tube moved aimlessly from side to side. Pathetic and embarrassing.
Yes, there's a metaphor in there somewhere...
My recommendation: bathroom vents are supposed to blow outdoors! Poorly taping them onto a receptacle high on a roof is probably a recipe for a problem down the road. But when the tubing comes apart, it really does need repair. There's no point in adding humidity where it does not belong. What would a better connection be? A Best Practice connection? Aluminum tape AND a well-tightened plastic strap. A dependable, strapping little fellow like the ones to the left. I have a jar full of them in my garage. Everyone should!
Jay Markanich Real Estate Inspections, LLC 
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560
