On one of my latest inspections I discovered that a bathroom fan vent did not terminate outside the attic space. The question always arises: Why does the vent need to go outside the attic?
You should never exhaust the bathroom fan directly into the attic. Your attic is not a temperature-controlled environment, is never the same temperature as your living space and generally closer to the temperature outside. What this means is that in colder weather, the vented air with moisture in the air will mix with the attic air causing condensation to form due to the warm air from the bathroom and it doesn’t have to be freezing for this to occur, however, just cool enough fall below the dew point. At that point discoloration can occur. Once this happens damage can occur to the roof decking and in extreme cases, cause mold to form! Although I cannot quote code during a home inspection, it is code to vent the fans outside the home.
On most inspections it is very difficult to determine if the vents actually go outside the home. On more modern construction the vents are installed before the insulation. On older homes, the vents were rarely ran outside the home, usually no vent was provided. Take the time to ensure the bathroom exhaust vent is done properly. This vent did not exit the home. At this point there is very little damage, mainly just staining. Left much longer and other issues could arise.
