Furnace Not Keeping House Warm in Greater Vancouver

When a furnace runs almost constantly but the house never reaches the set temperature, Greater Vancouver homeowners are often dealing with a combination of equipment and home envelope issues.

What This Symptom Means

A furnace that cannot keep up with heating demand may be undersized for the home, losing efficiency due to age or maintenance neglect, or fighting against heat loss through drafts, windows, or poor insulation. It can also mean a component is not operating at full capacity.

Common Causes

• Clogged air filter reducing heat output
• Dirty burners or heat exchanger reducing efficiency
• Duct leakage losing conditioned air to unconditioned spaces
• Home envelope issues — drafts, poor window seals, or inadequate insulation
• Furnace undersized for the home or a recent addition
• Flame sensor limiting burner run time
• Blower motor running at reduced speed due to wear

What Homeowners Can Check Safely

• Replace air filter
• Walk through home checking for obvious drafts near windows, doors, and electrical outlets
• Check that all supply vents are open and not blocked by furniture or rugs
• Look at outdoor temperature — furnaces are sized for typical winter conditions, not extreme cold snaps

When to Call a Licensed Technician

Some furnace issues require a licensed HVAC technician. Do not attempt to open gas lines, replace internal components, or reset persistent lockouts without professional diagnosis.

• Heat exchanger and burner efficiency inspection
• Duct leakage testing and sealing
• Blower motor speed and performance testing
• Heat load calculation to confirm correct furnace sizing
• Flue and venting inspection for draft issues

Frequently Asked Questions

Why can my furnace not keep up when it is very cold outside?

Most residential furnaces are sized to maintain a set indoor temperature when outdoor temperatures are at a typical winter low — for Greater Vancouver, usually around -5°C to -10°C. During unusual cold snaps, demand can exceed the system capacity. If it struggles regularly at normal winter temperatures, a service call is warranted.

Can duct leaks make my furnace seem undersized?

Yes. Studies suggest that duct systems in older homes can leak 20–30% of heated air into attics, crawlspaces, and wall cavities before it reaches living areas. This is a very common reason homeowners feel their furnace cannot keep up, even when the equipment itself is working correctly.

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