On Feb 9, 1:13�pm, "EXT" wrote:
"Walter Cohen" wrote in message

...

Due to logistical reasons in my attic I need to route the new bathroom fan
exhaust duct up through the roof instead of out the side wall. �It's also
a shorter run if I go vertically instead of horizontally.
I'll be buying 4" aluminum ducting so when I buy a hole saw to cut the
roof hole do I buy one that's 4" round, 4 1/4", or 4 1/2"?

Anything else I should do or watch out for?

Thanks.
Walter

For size measure the flange on the vent fitting you will be using on the
roof and add about a 1/4 to 3/8 to allow the clamp to fit into the hole.

I would not use a hole saw to cut through the roof. The tar in the shingles
will grab the hole saw of that size and tear the tool out of your hands, the
grit in the shingles will destroy the teeth on the hole saw. Take a jar lid
or some other template of the correct size and a Magic Marker to the roof,
use a drill to start the hole and cut along the line with a very coarse
tooth jig saw blade -- the blade will most likely be destroyed cutting the
hole and you will probably toss it when finished, but they are cheap.

I have installed several this way.

i would prefer to run exhaust thru sidewall..........

be certainto well insulate any exposed line in attic so condensarttion
doesnt cause water damage