Condensation in exhaust ducts

Prevent water from draining back through bath/hood ducts crossing cold attics by addressing routing, insulation, slope and termination.

VERT / GREEN = documenter/entretenir · JAUNE / YELLOW = vérifier avant travaux · ROUGE / RED = arrêter le DIY et faire valider.

Water drips from fan
Check condensation, insulation, slope and termination before dismissing the symptom. Long/crushed flexible duct
Reduce losses and pockets where water can collect. Uninsulated duct in cold attic
Verify continuous insulation/vapour control for the assembly. Exterior terminal clear
Inspect snow, damper and fastening yearly.

What the professional checks

Verify airflow, insulation and slope
Coordinate exterior termination

Official sources

CNRC — condensation de conduit en grenier RNCan — toitures et greniers

Checked: 2026-08-22

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Often-overlooked service interfaces

This section connects systems that cross utility, plumbing, HVAC, envelope and metering boundaries.

HVAC zoning and motorized dampers

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Commissioning and everyday safety

This section helps verify systems after work and document the values that make a home safer to operate.

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These details are small on a drawing but can control water, structure or durability.

Cold-pipe condensation