A 10-25 minute Canadian cold-climate check of a bathroom exhaust fan duct route, insulation, vapour-air seal, and exterior termination before ceiling insulation, board, or attic cover-up hides the detail.
8 items to check
These checklists are in development and testing. Information is for reference only and does not replace professional consultation. Data may contain inaccuracies. Consult a qualified professional.
If you notice an error, please email [email protected].
For a complete inspection, also consider:
Canada-specific pre-board review of rough-ins, air/vapour control, structure, and documentation before gypsum board or insulation hides the work.
Focused check of penetrations through exterior wall air/vapour control layers before board or insulation hides the details.
Bathroom exhaust should discharge to the exterior, not into a cold attic, soffit cavity, roof space, crawlspace, or other enclosed area. Exact termination rules and clearances depend on the adopted provincial code, local AHJ, roof or wall cap, and project design.
The duct route should follow the fan manufacturer's instructions and the project design, with compatible duct size, reasonable length, secure support, and limited bends. Local code or AHJ requirements may control duct material and installation details.
In a cold attic, warm humid exhaust can condense inside the duct. The route should manage condensation according to the fan, duct, termination, and project instructions, usually avoiding low pockets where water can collect or drain back to the fan.
Exhaust ducts passing through or near unheated attic space generally need insulation to reduce condensation risk. Required insulation level and vapour jacket details vary by province, project, duct product, and AHJ, so do not assume one universal R-value.
Duct joints should be mechanically secure and sealed with materials accepted by the duct and fan manufacturer, project specifications, and local code. Cloth duct tape alone is not a durable air-sealing strategy.
The ceiling penetration at the fan must maintain the air barrier and vapour control layer required by the wall and ceiling assembly. In cold climates, leakage around the fan box can carry moist indoor air into the attic even if the duct itself is correct.
The roof or wall termination should be compatible with the fan, duct, cladding or roofing system, and local code. Backdraft protection, exterior flashing, and location relative to intakes, openings, snow, and soffit ventilation depend on the project and AHJ.
Because bath fan duct defects are often hidden by ceiling board, vapour barrier, attic insulation, or roof work, the inspection record should show the route, insulation, seals, and termination before cover. Some projects may require mechanical inspection or manufacturer documentation.
Use this checklist when the bathroom fan box, duct run, vapour-air seal, insulation sleeve, and exterior termination are still visible. It is not a full HVAC audit; it focuses on the cold-attic condensation and air leakage risks that are difficult to fix after cover.
Canadian requirements vary by province or territory, adopted code edition, local AHJ, project design, and fan or duct manufacturer instructions. Treat the permit drawings, mechanical notes, provincial code, and product instructions as controlling.