Vinyl siding uses J channel at every siding panel end.
Why order a vent that needs more J channel applied?
These vents already have the J channel built in and ready to install.
The standard J channel on these is a 2 1/2" rear flange and 1" face to the J and spaced 1" apart.
This creates a full 1" x 1" pocket to receive the siding ends and give good coverage.
Siding needs room to expand and contract at a different rate than the wood wall.
Looking at the 16 x 16 x 1 octagon louver, from the front, it looks like any octagon vent.
But it is clear the back of the J channel is extending out past the face trim by 1 1/2".
From the side view, the depth of the receiving pocket is visible.
Now here is where it can get confusing.
Deeper vents can have the J Channel on the face of the vent and have the rest of the vent extend into the attic.
This 18 x 18 x 4 octagon vent has 2 1/2" of vent behind the J Channel.
Once installed, this is all that will be seen.
After the siding is installed, the face trim will be all that is visible.
Triangle vents can be set for siding J channel on the bottom and top of the vent.
Or the top of the vent can be set for soffit J channel.
This one is preset for siding on the bottom and soffit on the top.
These are options on the order form.
For this 36 x 36 x 1 Square Louver Vent, the J Channel was set for vinyl siding on all 4 sides.
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