Furnace outdoor vent blocked by snow in Greater Vancouver

Greater Vancouver does not get heavy snow every winter, but when a cold snap dumps it, the plastic vent pipes on a high-efficiency furnace can get buried or iced over. A snow-blocked vent will shut the furnace down on its safety controls, often on the coldest morning. Here is how to spot and prevent it.

Why Snow and Ice Stop a Furnace

High-efficiency furnaces vent through low, often ground-level plastic pipes, which makes them vulnerable to drifting snow, snow sliding off a roof, or ice forming at the termination from the furnace's own moist exhaust. If snow or ice blocks the intake or exhaust, the furnace cannot prove draft, the pressure switch stays open, and the unit locks out rather than running unsafely.

This tends to strike during exactly the weather you most need heat. Homes with vents on the shaded north side, under a roofline, or near where plowed snow gets piled are most at risk in the Lower Mainland and Fraser Valley.

• Furnace shuts down without heat during or after snowfall
• Snow drifts, roof runoff, or ice frosting the vent openings
• Vents on shaded or low walls are most prone to blockage
• Both intake and exhaust must stay clear for the furnace to run

Clearing Snow Safely and Preventing Repeats

You can safely clear snow and ice away from the exterior vent pipes by hand or with a soft brush. Gently remove the buildup from both openings and the surrounding area, and avoid chipping at ice directly on the pipe, which can crack it. After a snowfall, make checking the vents part of clearing your walkway.

If the furnace will not restart once the vents are clear, or if it keeps locking out, have a licensed technician inspect the venting and consider whether the termination needs to be raised or relocated. If you ever smell exhaust indoors, leave the home and call your gas utility's emergency line first.

• Gently brush snow and ice away from both vent openings
• Do not chip ice directly off the plastic pipe
• Check the vents after each snowfall along with your walkway
• Ask a technician about raising the termination if it blocks repeatedly

Frequently Asked Questions

Why does my furnace quit when it snows?

Snow or ice blocking the intake or exhaust pipe prevents the furnace from establishing proper draft, so it locks out on its safety controls instead of running unsafely. Clearing the vents usually lets it restart.

Can I clear snow off the vent pipes myself?

Yes, gently. Brush snow away from both openings by hand or with a soft brush. Avoid chipping ice directly on the plastic, since that can crack the pipe, and never force tools into the openings.

How can I stop this from happening every snowfall?

Make the vents part of your snow-clearing routine and keep piled or plowed snow away from them. If the vents block repeatedly, a technician can advise on raising or relocating the termination above typical snow levels.

Is a snow-blocked vent dangerous?

The furnace is designed to shut down rather than run with blocked venting, which is a safety feature. Still, if you ever smell exhaust indoors, leave the home and call your gas utility's emergency line before doing anything else.

HeatLand Heating & Cooling is a licensed and insured, TSBC-certified HVAC company serving homeowners across Greater Vancouver. Our technicians diagnose the real fault, explain your options in plain language, and complete the work safely and to code.

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