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

V26

Often-overlooked service interfaces

V26 connects systems that cross utility, plumbing, HVAC, envelope and metering boundaries.

HVAC zoning and motorized dampers

V31

Commissioning and everyday safety

V31 helps verify systems after work and document the values that make a home safer to operate.

Condensing-appliance condensate

V47

V47 interfaces not to miss

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

Cold-pipe condensation