In April of 2023 I had the opportunity to observe benefit of Roof Penetration Adapters of through-roof bath and kitchen fan ducts at roof caps, in my own home, now a rental.
I placed second-layer shingles by myself in the cool, wet weather. There was no cause to spend in excess of an additional $10,000, for a hired tear-off.
I chose the lightest-color shingles I could find, hoping to avoid need of air conditioning while I wait for better opportunity with heat pumps. Isn't white better year-round? There is little demand for this color.
Here, I confronted the steel roof cap of the 6" steel duct from the kitchen exhaust fan, Panasonic in-line. The roof cap is Famco PB6BK, modified with maximum circular enlargement of the back opening, salvaging the backdraft damper of the 6" pipe stem. See my as-always surprising treatment of the roof cap as merely a rain cover. There is no need to deeply tuck the cap under shingles. Not knowing the full story, a roofer will see this as error. That thing is going to leak!
A separate Roof Penetration Adapter here seen inverted, is under that roof cap, tucked even under roof membrane. A 6" pipe male end tightly engages the ID. My adapters for now are 12" square aluminum plates spinning-formed to about 1" tall upward stem. $25 each, hard work, not sustainable. Production adapters would be stamped inexpensively. I or some other fabricator, await demand. Reader: please get interested.
The Famco backdraft damper is now riveted to the spun-aluminum 6" roof cap.
There are no leaks anywhere in the thirty year old expired shingling I applied as a tear-off at house age fifty years, replacing much rotted 1x8 shiplap with a reserve of lumber found in the attic. The durable underlayment is 20 pound felt nowhere brittle, overlaying the penetration adapter of the four remodel fan ducts that I had installed over a span of twenty years; this the most recent. I trust the penetration adapter, now buried one layer deeper, to protect against leakage at any layer, for the life of my new reroof. Just snip the new shingles about a 6 1/2" circle. Roof cement at-the-ready for any first-layer rebuild, isn't of value here.
Reset the roof cap, now with less-pretty alignment with the shingle pattern.
With little nibbling of top-layer shingles, the rain barrier hinges down, perfectly aligned with the duct.
Here is a job photo from a customer installation of a Famco PB8BK, with more challenge from hacked-in termination of a 6" kitchen exhaust with needless enlargement to an 8" cap then leaking.
The 8" penetration adapter with 12" square surround is tucked under scrap sheet metal or shingle that reaches as high as possible, directly against the underlayment, for full shingle effectiveness.
This is far better than simple jamming-in of a roof cap, which had leaked. If there is a second layer of shingles someday, this roof cap will still work with no diminished effectiveness.
See visible, smart use of appropriate gasketed screws.
