Insufficient insulation is among the most typical causes that water stains and mildew type round a air flow fan within the rest room. With out insulation across the fan and vent pipe, the nice and cozy, moist air that the fan is pulling out of the lavatory might bump up towards the chilly air surrounding the duct and within the attic house. This causes the moisture to condense on the steel within the vent pipe, finally amassing on the drywall within the ceiling close to the fan — and doubtlessly inflicting staining and mildew formation.
One preventative choice is putting in ductwork for the vent fan that has pre-wrapped insulation round it. That is the best choice when putting in a brand new exhaust system in a toilet. For an current set up, although, you would need to climb into the attic house to wrap the vent pipe with insulation. Earlier than buying insulation to wrap round it, examine the house for the present set up. It could have already got insulation — if so, the water staining across the fan is from one other supply. If that you must add insulation to the pipe, the best choice is to uninstall the vent, pulling it misplaced so you possibly can wrap it earlier than reinstalling it. You would additionally wrap it in insulation whereas leaving it in place, however that is difficult work to do in a good attic house. A handyperson ought to be capable to do the give you the results you want if wanted.