The House Detective: by Barry Stone, Certified Home Inspector
Dear Barry: : Our laundry is located on the second floor, directly adjacent to the bathroom. Whenever I run the dryer, the bathroom becomes very humid if the door is shut. I’ve also noticed something like black soot on the bathroom walls. I wash it off, but it always comes back. What could be causing the humidity and the soot, and what can I do to resolve this? Debbie
Dear Debbie: Here are two possibilities: The vent duct for the clothes dryer may be connected to the bathroom vent duct in the attic. This would allow steam from the clothes dryer to enter the bathroom through the ceiling vent.
Another possibility is disconnection of the dryer vent inside the wall or ceiling of the bathroom. This would cause the moisture from your clothes to vent into the wall or ceiling cavities, raising the humidity in that room.
Another concern is that the “soot” on the walls could actually be black mold, caused by the excessive moisture condition. If so, this would raise health concerns for your family.
To evaluate and resolve this situation, three things need to be done:
1) A licensed contractor should investigate the path of the dryer vent to determine whether it is disconnected or not properly vented to the exterior.
2) The wood framing should be inspected to determine whether moisture exposure has caused fungus infection and dryrot.
3) The area should be evaluated by a qualified mold inspector to determine if mold is the problem and if mold remediation is needed. Air samples should be taken from wall cavities to determine whether there is mold behind the drywall.