Furnace Not Heating Upstairs in Greater Vancouver

An upstairs that stays cold while the main floor heats normally is a very common issue in two-storey Greater Vancouver homes — and it is usually a combination of duct design and natural air movement physics.

What This Symptom Means

Heat naturally rises, so logically an upstairs should not be cold. When it is, it usually means that supply air is not reaching those rooms in adequate volume, or that the rooms are losing heat through the exterior envelope faster than supply can compensate.

Common Causes

• Long duct runs to upstairs losing supply pressure
• Undersized supply ducts to upper floor registers
• Duct leaks in the upper floor branch reducing delivery
• Upper floor registers partially closed from previous adjustments
• Upstairs rooms with more exterior wall and ceiling exposure losing heat quickly
• Furnace blower not powerful enough for the duct run length to upper floor

What Homeowners Can Check Safely

• Fully open all upstairs supply registers
• Check for blocked registers — furniture, rugs, or drapery over floor registers
• Partially close main floor registers to redirect pressure upstairs

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.

• Duct airflow measurement on upper floor branches
• Duct sealing and insulation in attic duct runs
• Blower speed adjustment if motor supports multiple speeds
• Zone damper installation to redirect supply to upper floor during heating cycles
• Insulation assessment for upper floor exterior walls and ceiling

Frequently Asked Questions

Can I add a booster fan in an upstairs duct to get more heat?

Booster fans are available but require proper installation to work effectively. Installed in an undersized duct run, they can increase airflow to a distant room. However, they must be matched to the system and properly controlled to avoid creating pressure problems elsewhere. A technician can assess whether this is the right solution.

Why is my upstairs cold only at night?

Overnight, the outdoor temperature drops and exterior walls lose heat more quickly. Upstairs rooms with more exterior exposure (particularly those under the roof) will feel this most noticeably. Setting the thermostat a degree or two higher at night, or using programmable thermostat scheduling, helps maintain comfort on upper floors during the coldest hours.

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