I flagged attic moisture or frost accumulation in nearly 40% of inspections this winter, with the pattern concentrated in homes built between 1985 and 2005 across Quispamsis and Rothesay. The cause is almost always the same: one or more bathroom exhaust fans dumping warm, humid air directly into the attic space instead of venting it through the roof or a gable wall to the outside.
Building codes have prohibited venting exhaust air into attics, crawl spaces, or any interior area of a building for decades. But many homes built before the mid-1990s were not held to the same enforcement standards, and even in newer homes, shortcuts during construction are common. The fan gets installed, the duct gets run into the attic, and nobody routes it the last few feet to the exterior.
In a Maritime winter, the warm moist air from a hot shower hits the cold underside of the roof sheathing and condenses. If the temperature is low enough, it freezes. When it thaws, that moisture drips onto the insulation below, reducing its effectiveness and creating conditions for mould.
What the fix looks like
A qualified contractor extends the existing duct through the roof or gable wall and adds a proper termination cap with a backdraft damper. In most cases it is a half-day job. The cost is typically under $500 per fan.
If your listing is a 1990s-era home in the KV, ask the seller whether the bathroom fans vent to the outside before you schedule listing photos. Addressing it proactively is a $300 to $500 conversation. Addressing it during a negotiation is a $3,000 to $5,000 conversation.