When an Alberta cold snap hits, your furnace doesn’t get a break, it runs around the clock to keep your home safe and warm. But extreme weather is also when heating systems are most likely to fail. That’s when we start getting “no heat” calls, often from homeowners waking up to an icy surprise and a house that’s dropped to 12 degrees or lower overnight.
The good news? Most furnace issues during deep freezes are preventable. Here are the top three causes of mid-winter breakdowns, and what you can do to avoid them.
A clogged or dirty filter is by far the most common cause of furnace failure during extreme cold. When your system can't get proper airflow, it starts to overheat. That can trigger a safety mechanism that shuts the furnace down entirely.
This often happens without warning. When it’s only mildly cold outside, your furnace may be running at half-capacity without you noticing. But as soon as the temperature drops, the system can’t keep up and you’re left without heat when you need it most.
Quick fix: Check your filter every 30 days during the winter and change it when it’s dirty. A fresh filter ensures your system can move air properly and helps prevent overheating.
Another top reason for furnace shutdowns in cold weather is a dirty flame sensor. This small component helps ensure your furnace ignites safely. But over time, it can build up residue that prevents proper function, leading to your system shutting off intermittently or completely.
The tricky part is you may not even know it’s happening. When outdoor temperatures are moderate, a furnace can “get by” with a dirty flame sensor. But once the cold sets in, that margin disappears and your furnace fails.
Solution: Routine furnace maintenance includes cleaning or replacing the flame sensor. It’s a simple but critical part of a professional tune-up and can save you from a mid-winter no-heat emergency.
In high-efficiency furnaces, exhaust vents can freeze over during prolonged cold snaps. This blockage triggers a safety shutdown to prevent dangerous gases from entering your home.
We’ve seen this happen frequently during polar vortex events or sudden drops in temperature. It’s especially common when snow, ice, or even frost builds up outside around the vent area.
Prevention tip: Keep your furnace’s exterior vents clear of snow and ice. If you’re not sure where they are, your technician can show you during your next service appointment.
All of these issues come down to one thing: your furnace is working harder and longer in extreme cold. If there’s a weakness in the system, like a dirty component, it’s more likely to show itself when the furnace is under pressure.
Plus, many homeowners don’t notice furnace problems until the house starts to feel cold. By the time you realize there’s no heat, the system may have already been off for hours.
The best way to prevent furnace breakdowns in extreme weather is simple:
It’s not about changing your behaviour, it’s about understanding how your system works and taking simple steps to support it.
Be Winter-Ready with A1 Heating & Cooling
At A1 Heating, we help St. Albert homeowners stay warm through every freeze-up. If you haven’t had your furnace checked this season, there’s still time to book a tune-up and avoid the stress of emergency calls.
Call us or book your
furnace checkup online today. Because when the temperature drops, your furnace can’t afford to fail.
