I have 4 bathrooms where the bath exhaust fan were connected to 4" sheet
metal ducts, when I remodeled the bathrooms I chased the ducts and none of
them actually vent outside, they just vent into the attic.
I was able to connect one exhaust fan to an abandoned vent through the roof,
the vent was originally intended for a kiln which I removed. Now I have
three bathroom exhaust to deal with, all 4" ducts.
I am trying to avoid punching holes through the roof so looking for an
alternative. The house's roof has an overhang about 5 feet wide, and the
soffit is made of wood panels. My idea is to vent through the soffit.
What I am thinking of doing is to cut a 4" diameter hole from the underside
of the soffit panel. Once this is done, then I will take a 90 degree 4"
duct elbow, connect it to a flex coiled aluminum duct with stainless steel
clamps, and push the elbow from inside the attic towards the hole (I cannot
crawl too close to the hole, as the space is real tight in the overhang
area) once I am near the hole I can go back outside, and crab the elbow and
pull may be about half an inch of that elbow to the outside.
Now here is where I am not sure what to do. Is there some sort of collar or
vent cover that I can clamp on glue onto that duct hole which is now facing
down? Something that would normally be closed but will only open when there
is positive pressure from the fan? This would have to be something that is
spring loaded right? I don't want to just leave a 4" wide hole there as
critters would just go in. I guess I can cover it with a fine mesh of some
My question is - will this work? To have a exhaust vent outlet that face
down instead of up? If so, is there any sort of special vent cover designed
for this situation?