On Feb 23, 7:48 pm, "MiamiCuse" wrote:
OK this is probably a really stupid question but I thought I ask...

I would like to get a high power exhaust fan for my bath. Most of them use
6" duct to vent to the roof. My roof vent is 4" and I don't want to change
it.

Can I get a fan for 6" and then use a reducer to go from 6" to 4" duct then
to the vent?

Will this make it work "better" than a regular 4" exhaust fan?

I think this is a bad idea...

MC

Ideally one should use 6" duct all the way (including roof vent) for a
fan with a 6" outlet.

A 6" to 4" reducer will add "effective length" to your duct run as
will your 4" roof vent.


Before you go through all the added complication of dealing with using
6" fan on a restricted ducting system...how about looking into an
adequate fan (cfm & noise level) that is designed to work with a 4"
duct?

Depending on the size of the bathroom & moisture loading, a 4" fan
could work just fine.

Over sizing the fan wrt to cfm is not necessarily a good thing.

cheers
Bob