I see this quite a bit in day-to-day inspections. Moisture stains around bath vent fans. What causes it and what can be done about it? If the bath fan ducting that runs through the attic to the roof deck is not insulated you are almost certainly going to see this happen. Even if your duct is insulated you might still see it occasionally. During the winter when your bath fan is running, warm moist air from the home is traveling through this duct. An uninsulated duct almost instantly will start the process of condensation where air from the interior of the home condenses on the interior and drips back down to the fan housing. From here it wicks into the drywall surrounding the fan housing. But the duct is insulated, this shouldn't happen... Well, in theory, yes it shouldn't happen but if a fan is left on for an extended period of time with an insulated duct the R-value is not substantial enough to keep condensation from occurring and you guessed it... water spots.
So what can be done about it? If it is not insulated obviously get some insulation on the ducting, be it an insulation wrap or have the pipe sleeved with insulation. If it is insulated simply install a bath fan timer in place of the standard switch. This will limit the time the bath fan can run and stop those times when the kids leave the fan on for 3 hours when it is -25 degrees outside. This can also help increase the efficiency of the home, conditioned air is not being pumped out of the home for hours on end equating to more dollars in your pocket. This is an inexpensive step a homeowner can take so an expensive ceiling repair doesn't need to be made down the road.
If you have any topics or ideas you would like to see in a future edition of Homeowner Tidbits feel free to drop me an email at lfreng@inspectionwerx.com and as always "Get the best of US before your new home gets the best of YOU!
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