I recently had a bathroom ceiling light replaced with a light-fan. An electrician did the installation and the roofer added a roof vent and the new fan is vented
out the roof. The light and fan are on separate switches. The issue: we
selected the 70 CFM light and fan because it has a plastic (rust-proof) frame
and looks good, however at 3.5 SOMS the fan is quite noisy.

I am looking for opinions on adding an in-line fan in the attic, plus two
dimmer switches in the attic that can be used to 1) slow down the unit's own
fan to make it quieter, and 2) adjust the in-line fan speed for an acceptable
noise level, while making sure that shower steam is being vented from the room. Both fans would be on the same circuit.

Or would this be the preferred solution: add and in-fan and disconnect the
unit's fan.

Thanks for your advice.

 

Removing the fan from the unit (the blades will still turn if you simply snip the wires) and installing a remote fan should be all you need to do. It's always a good idea to have the fan on a timed switch so that it runs a sufficient amount of time after a shower.

 

OKAY, then that will be the plan: remove the unit fan as it will have no purpose, and install
the in-line fan in a vent pipe between the unit and the roof vent so that the sounds will be
more like moving air and less like a fan in the room. Thanks again.