wrote:
I am installing an exhaust fan in my bathroom, which will vent through
the roof about 2.5 feet above the unit. I have an exhaust hood in my
kitchen, and when I stand by the stove I can hear the traffic out back
because the outside vent on the roof faces the traffic and acts like a
collector to bring the noise into the house.

My bathroom vent will also face the road, and I don't want to carry
that noise into the house. What kind of duct will be the quietest? I
think the thin, ridged metal tubing would be the loudest. I'm
thinking the flexible stuff (like dryer vent hose) will be quieter?
I know it has more resistance but its a short run and the fan is
plenty powerful for the room its in. But I was definately going to
insulate the pipe, is the flexible stuff insulated? It felt pretty
thin when I was looking at it in the store.

Also I was planning on getting a plastic vent for the roof, I think
that should be quieter than a metal one?

Thanks for any help.
-Ryan

The quietest would likely be some flexible duct, but that is also not
very efficient. I think I would try spraying the inside of metal duct with
the type of stuff used for undercoating cars. This should work well, be
cheap and may even reduce condensation inside the pipe. You might also
check out: http://www.soundproofing.org/ and see if they have any ideas
there.

Note: do not use the undercoating trick for a range hood vent. That
would be a fire hazard.

--
Joseph Meehan

Dia duit