Bathroom vent fan ductwork insulation.
Attic insulation over bathroom fan.
Seal holes in the fan housing with caulk sealing putty or metal tape.
I think you need to go into attic regardless as the fan housing probavly has brackets attached to the attic joists.
Install the fan then seal around the fan with caulk or canned spray foam.
Always cover the tops of the ceiling joists to make sure the insulation is deep enough to reach your target r value and to prevent thermal bridging the heat loss that occurs through the wood framing.
Mar 8th 2018 2 12 pm.
If bath fan ducting isn t properly insulated the moist air from your house will condense inside the duct.
Work from the perimeter of the attic toward the door or hatch so that you don t trample all over the insulation you just put in.
Never exhaust your bath fan into your attic.
If you see that your duct isn t insulated at all pick up duct insulation at the home center.
You may find that the insulation simply needs to be refastened.
If that moisture is released into your attic space it can cause significant damage to your insulation floors ceilings walls joists and roofing structure.
The air being removed from your bathroom is warm moist air.
Seal around the exterior fan duct vent with caulk or a pre made exterior wall gasket.
Another approach could be an insulated hvac duct approach.
But some consider it somewhat flimsy and may not support the weight of insulation over any distance.
In un conditioned space such as an attic where otherwise your fan duct will be exposed to cold attic air in winter use insulated solid metal ducting or insulated flex duct.
You can buy a bags of cellulose from lowes fluff it up into a garbage bags and dump into attic after you are done on top of the area where you disturbed insulation.
Insulate the bathroom exhaust vent fan ducts.
There are several options available for the ducting like flexible aluminum ducting.
It is very important that you exhaust your bathroom fan outside.
The first step is to head to the attic.