Should the bathroom exhaust go through the roof in Calgary?

Bathroom exhaust ventilation is mostly a mechanical and building-code question rather than a roofing one, so this sits at the edge of Roof IQ's scope. The short roofing answer: yes, routing the duct through the roof is a common and generally acceptable termination point in Calgary, but the penetration itself matters a great deal to your roof's performance.

The Roofing Part That Matters

When a bathroom exhaust duct exits through the roof, it needs a proper roof vent cap, and the flashing around that cap is one of the more common leak points on Calgary homes. Calgary's freeze-thaw cycle (roughly 128 cycles a year by City of Calgary climate data) works at every imperfect seal. A poorly flashed vent boot cracks, lifts or separates, and water tracks down the duct or along the sheathing before you see a stain on the bathroom ceiling. When a roofer is replacing your shingles, replacing the vent boots and flashings at the same time is standard practice; reusing old rubber boots on a new roof is a common mistake worth avoiding.

The penetration also needs to be sealed against ice damming. Calgary sits in a climate with enough heating degree-days that the National Building Code requires eave protection (ice-and-water shield) extending at least 900 mm up the slope and to a line at least 300 mm inside the inner face of the exterior wall. A roof vent located near the eave sits in that zone and needs careful integration with the underlayment.

Never vent a bathroom exhaust into the attic. Warm, moist air dumped into an attic causes frost in winter and mould in summer, and it shortens the life of your sheathing. The City of Calgary's guidance on attic ventilation is clear that the attic space needs to stay dry; adding a moisture source defeats the purpose entirely.

Where the duct terminates, whether through the roof or through a soffit or wall, is a question for your HVAC or mechanical contractor and your building permit office. The City of Calgary issues building permits for mechanical work of this kind. Roof IQ covers the roofing penetration side; the duct routing, duct sizing and mechanical code requirements are outside this scope.

If you are having roofing work done at the same time, ask the roofer to inspect and replace any existing vent boots and to confirm the flashing is properly integrated with the ice-and-water shield and underlayment. That is a reasonable line item to see spelled out in a written quote.

For the mechanical and ventilation side of this question, a licensed mechanical contractor or the City of Calgary's permit office is the right call. For other trades, you can find contractors through the Calgary Construction Network at calgaryconstructionnetwork.com.