A dryer vent through the roof is a very dangerous thing.
I have written about dryer vents before, in many contexts. Including through a roof!
But this one is so dangerous I have to reiterate my points.
I always prefer to see a dryer vent on the side of a house. Even if it's high.
How do you know a dryer vent needs cleaning? YOU HAVE TO LOOK AT IT.
How do you clean a dryer vent? MANUALLY.
This dryer vent is NOT visible from the ground. How do you know it needs cleaning?
With great effort.
This house leaves four choices to clean the dryer vent -
1. A climb up in front and traversing a metal roof. They can be slippery.
2. A 40' ladder from the rear of the house, with another trip over the ridge of the house, negotiating fairly steep aspects up, over and down. THEN you have to go back up, over and down the roof to get onto the top of a 40' ladder to climb down! Yikes!
3. Slither out a bedroom window, walk along a ledge on top of a metal roof, and climb up a fairly steep shingled roof 12' to get to this vent.
4. Hire somebody! And that would necessitate two people with a long ladder. Not cheap.
That is all ridiculous!
Look at this vent. It is 100% clogged! Someone has been up here before because I see roof tar above and beside the vent. Is this the builder's "installation" job? Did it leak and is this the "fix?" The house is seven years old. Has this vent ever been cleaned?
This roof is the third floor of the house. The laundry room is on the first floor. Looking at the house geography from inside the exhaust tubing servicing this vent goes straight up! It is not accessible from inside the house. I could not see it from the attic, so it is difficult at best to get at from inside there.
It must pass through a portion of the attic. Is it insulated?
What happens when it snows deeper than 3"? This vent is clogged even more!
In my opinion a dryer vent through a roof is less than smart. How much less depends on its placement.
My recommendation: all in all this is a dangerous vent, not just now but in the years to come. How often should a dryer vent be cleaned? When it's clogging! I always look for the dryer vent on home inspections. It is important to see where it is and if it needs cleaning. We fortunately found this one, and only because I took a risk and went out a window to see if it was where I suspected!