My furnace makes a banging noise during chinooks when the temperature swings 20 degrees overnight. Is this normal or a problem?

Banging noises during chinooks are extremely common in Calgary furnaces, but they shouldn't be ignored. The rapid temperature swings that Calgary is famous for put unique stress on heating systems, and that banging is usually your ductwork expanding and contracting as it heats up and cools down rapidly.

Ductwork expansion and contraction is the most likely culprit. When your furnace kicks on during a chinook temperature swing, the metal ducts heat up quickly and expand. As they cool, they contract, creating those distinctive banging or popping sounds. This is particularly noticeable in Calgary because our chinooks can swing temperatures 20-30°C in a matter of hours – far more extreme than most heating systems experience elsewhere in Canada. Older homes with galvanized steel ducts tend to be noisier than newer homes with insulated flexible ducts.

However, not all banging should be dismissed as normal. If the sounds are new, getting louder, or accompanied by other symptoms like uneven heating, higher energy bills, or visible duct movement, you may have loose ductwork connections, undersized ducts, or mounting issues. The extreme temperature cycling in Calgary can cause duct hangers and connections to work loose over time. Additionally, if your furnace itself is making banging sounds (rather than the ducts), this could indicate issues with the heat exchanger, blower motor, or gas valve that require immediate professional attention.

Calgary's climate makes proper HVAC installation critical. Our temperature extremes mean ductwork needs adequate expansion joints, proper support, and sometimes insulation to minimize noise. High-efficiency furnaces (96%+ AFUE) that are standard in Calgary can also create different expansion patterns than older units. The rapid on-off cycling during mild chinook weather can exacerbate these sounds.

When to call a professional: If the banging is coming from the furnace unit itself (not the ducts), if you smell gas, if heating performance has declined, or if the sounds are new and concerning. A licensed gas contractor can inspect your system and ensure all connections are secure. For ductwork issues, an HVAC contractor can add expansion joints, improve supports, or recommend insulation solutions. Remember that all gas appliance work in Alberta requires licensed contractors and inspection by Safety Codes Council of Alberta officers.

Next steps: Monitor when the sounds occur and whether they're from ducts or the furnace itself. Schedule a maintenance inspection if you haven't had one recently – Calgary's extreme conditions mean annual furnace maintenance is essential for both safety and efficiency.