As we put more laundry rooms on the second floor of homes, the shortest path to vent the dryer exhaust to the outside may be up through the roof. And that in itself isn’t bad. Dryers really don’t like to push air uphill, but if done correctly, these types of vents can be very efficient. Where the problem comes in is using the right type of vent.
Let me explain. When you look up on your roof, you will see all kinds of exit points. Some are plumbing, some may be vents like for the dryer or an upstairs bathroom fan and others will be simple attic vents. Most of these vents used for years and on older homes have traditionally been made of metal. But as another one of those cost saving measures when building or remodeling a home, most vents used these days are made of plastic. And like most other things plastic, don’t have the longevity you would expect of something that is sitting up on your roof.
I suspect the thinking from the builder is the roof will need to be replaced in 25 years anyway and the vents will be replaced at that time. Again with plastic I would guess. The problem it creates is these plastic vents when used for dryers are constantly subjected to heat and lint. Not to mention the sun beating down on them and then the rain. Well in this part of Oregon more rain then sun, but they must deal with either or on a daily basis.
Once this plastic become less flexible or even brittle, the chances of having the ducting come loose in the attic or the damper not opening properly increases and then you begin to have dryer issues. And these issues may have nothing to do with the dryer itself, but everything to do with the venting, but since the vent is on the roof, you may never even know it.
Fortunately there are still vents made of metal and even those, such as the one installed on this job, that are metal, made in America and designed specifically for venting dryer exhaust. The good thing is these can usually be retrofitted without much hassle other than writing a check, and can go a long way toward improving the airflow of your dryer. And the fact it is made of metal, it can take the daily punishment of the dryer heat plus the outdoor elements. What more could you want?