Chuck wrote:
> Going to have to install range hood with outside exhaust (through the
> roof) this weekend...

Why through the roof, why would you want to cut a big hole in your nice
brand new roof? If possible you're always better off with a
residential exhaust exiting through a side wall with the ductwork
aiming downward. My exhaust duct goes up through a kitchen cabinet and
into the attic where it travels horizontally about eight feet and exits
downward through the soffit... this arrangement also makes it easy for
me to maintain the system myself, I can easily remove all the ductwok
from inside the attic and take it outside to clean if necessary.
Ductwork exiting a peaked roof tends to suffer from down droughts as
even a slight breeze is amplified by the venturi effect as it travels
over a pitched roof. For such a system to work properly you'd need a
vent pipe that extends at least three feet higher than the roof ridge,
very ugly. Those flush mount mushroom looking thingies don't work very
well on many counts, the exiting exhaust grease will stain the roof
too, badly... within a year you'll have a big ugli stain on your nice
new roof, and everytime it rains that stain will expand and also run
down to the eves... this won't look pretty. You don't want to place
any extra holes in a roof, just another place for a leak to develop.