Where should a New Brunswick bathroom fan duct terminate?

A bathroom exhaust fan in New Brunswick must duct to the exterior of the building — never into an attic, wall cavity, crawlspace, or soffit. This is one of the most commonly violated ventilation requirements in NB homes, and it causes serious moisture damage when ignored.

The National Building Code of Canada 2020 (adopted in New Brunswick effective May 1, 2025 for new applications) requires that all bathroom exhaust fans terminate at an exterior wall cap or roof cap with a backdraft damper. The damper prevents cold air from flowing back into the duct during NB's brutal winters — when temperatures regularly hit -25°C to -30°C inland, a missing damper means a frozen duct and condensation problems.

Duct routing matters as much as the termination point. The shortest, most direct path to the exterior is always best. Every 90° elbow adds roughly 5 feet of equivalent duct length to the system's resistance. For most NB homes, the practical options are through an exterior wall (ideal for fans on exterior walls) or up through the attic and out a roof cap. If routing through the attic, the duct must be insulated — uninsulated duct in a cold NB attic will cause condensation inside the duct itself, dripping water back into the fan or ceiling. Use rigid metal duct where possible; flexible duct works but must be kept taut and supported to avoid sags where moisture collects.

Roof terminations need to be at least 12 inches above the roof surface and positioned to avoid snow burial — a real concern in northern NB communities like Edmundston and Campbellton, which regularly see 300–400 cm of snow annually. Soffit termination is specifically prohibited because exhaust air re-enters the attic through soffit vents, defeating the entire purpose.

In older NB homes — particularly post-war bungalows and 1970s–80s splits common in Riverview, Quispamsis, and suburban Fredericton — it's very common to find bathroom fans that were originally vented into the attic with a piece of flex duct just hanging loose. This was accepted practice decades ago but has caused widespread attic mould problems across the province. If you're buying or renovating an older home, checking the bathroom fan termination should be near the top of your list.

Fan installation itself is generally a DIY-friendly project for the duct and housing work, but the electrical connection requires a licensed electrician — TIS (Technical Inspection Services) licenses all electricians in New Brunswick, and an NB Power wiring permit is required for the electrical portion. Don't let anyone tell you otherwise.

A good next step: go into your attic (safely, in warmer months) and trace where your bathroom fan duct actually goes. If it's not connected to a proper exterior cap with a damper, that's worth correcting before next winter. You can find experienced ventilation and renovation contractors in the New Brunswick Construction Network directory to handle the full job properly.