Re: Bathroom fan louder since insulation installation
If the insulation has caused the vent to collapse, it will block airflow which will increase the loudness. Turn on the fan, then check the vent outside to see if air is coming out. If none is coming out, or it's coming out wimpily, it's probably blocked.
One other thing to check is the damper on the outlet of the fan housing. You may need to remove the blower and motor from the housing to access the damper. Sometimes you'll get a buildup of greasy dust that causes the damper to stick.
While you've got the fan apart, give it a good cleaning. Don't get the motor wet; just use a vacuum. If the impeller (fan blades) can be removed from the motor, wash the impeller. Lubricate the motor bearings with a light oil such as 3-in-1. Just a tiny drop on each bearing is sufficient.
If that doesn't resolve the issue, your best bet is to just run a new exhaust duct.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.