Frozen or Blocked Furnace Vents
High-efficiency furnaces breathe through plastic pipes on an outside wall or the roof. In Winnipeg winters, those pipes can freeze up or be buried by snow.
Request an HVAC technicianWhy it happens
The exhaust is warm and full of moisture, which can freeze around the pipe end in extreme cold. Drifting snow, snow banks from shovelling and ice falling from the roof can block the pipes too.
Signs
The furnace starts, then shuts down; a flashing code on the control board; frost or ice built up around the vent pipe ends.
Clearing them
Gently remove snow and frost by hand or with a soft brush. Don't chip at the pipes with tools, which can crack them.
After clearing
Turn the furnace off and on to reset it. If it won't restart, get a technician.
Prevention
Keep the area around the vents clear when shovelling, and watch them after storms and during long cold spells.
Vent placement
Vents too close to the ground or under a roof edge are prone to blocking. A technician can sometimes extend or relocate them.
Don't cover them
Never cover vent pipes to keep snow out; they need to breathe.
More help
See furnace repair.
Condensate lines
High-efficiency furnaces drain water through a condensate line. If it freezes or clogs, the furnace can shut down. Lines should never run through unheated spaces.
Roof vents
Some furnaces vent through the roof instead of a wall. Snow and ice on roof vents are harder to check; leave roof work to a professional.
Water heaters too
High-efficiency water heaters often vent the same way and can block for the same reasons. Check their pipes at the same time.
Snow blowers and plows
Don't blow or pile snow against the side of the house where vents exit. A snowbank can cover them overnight.
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