How do I know if my bathroom fan is vented outside or into the attic?

The easiest way to determine if your bathroom fan vents outside is to go into your attic and trace the ductwork from the fan to see where it terminates - it should connect to a roof or wall vent, not just dump air into the attic space.

Start by locating your bathroom fan from inside the attic. You'll see a round or rectangular duct (typically 4-6 inches in diameter) connected to the fan housing. Follow this ductwork carefully - proper installation means it should run directly to either a roof vent (you'll see it exit through the roof decking) or a soffit/wall vent on the exterior of your home. The duct should be insulated to prevent condensation, especially important in Toronto's climate with our cold winters.

Warning signs of improper venting include ductwork that simply ends in the attic space, connects to a soffit vent (which can cause moisture problems), or terminates near attic vents. You might also notice excessive moisture, mold, or frost buildup in your attic during winter months if the fan isn't properly vented outside. In Toronto's older homes, particularly century homes in neighborhoods like Cabbagetown or The Annex, it's unfortunately common to find bathroom fans that were improperly connected during renovations.

From outside your home, look for a dedicated exhaust vent on your roof or exterior wall that corresponds to your bathroom location. These vents typically have a damper or louvers that open when the fan operates. You can test this by turning on your bathroom fan and having someone watch the exterior vent - you should see the damper open and feel air movement.

Professional assessment is recommended if you're unsure, as improper bathroom ventilation violates the Ontario Building Code and can cause serious moisture damage, mold growth, and structural issues. This is especially critical in Toronto's humid summers and cold winters. A licensed contractor can also ensure the ductwork is properly sized, insulated, and terminated according to code requirements.

Next steps: If you discover your fan vents into the attic, this needs immediate correction. The work involves running new ductwork and installing a proper exterior vent - typically a half-day job for an experienced contractor, with costs ranging from $300-800 depending on accessibility and routing requirements in the GTA market.