Why Does My Furnace Take a Long Time to Heat Up the House?

Have a heating or cooling question about your home? Call (604) 359-1081 or request a free written quote.

What's actually slowing your furnace down

Slow heating rarely means the furnace is broken. More often, warm air isn't moving efficiently, or it's escaping as fast as your furnace can produce it. A handful of causes account for most complaints we see across Metro Vancouver homes.

• Dirty air filter: A clogged filter chokes airflow, so less warm air reaches your rooms and the furnace works longer to hit the target temperature.
• Closed, blocked, or leaky ducts: Furniture over vents, closed dampers, or gaps and disconnected joints in ductwork can send heat into your crawlspace or attic instead of your living space.
• Poor insulation and air leaks: In older Vancouver-area homes, heat lost through drafty windows, uninsulated attics, and rim joists means the furnace runs long just to keep up.
• Thermostat placement or settings: A thermostat in a cold hallway or near a draft can misread the room, and a large single jump in setting (say 15 to 22 degrees) simply takes time.
• An aging or undersized furnace: Older units lose efficiency, and a furnace that was undersized for the home never had the output to heat quickly.
• A furnace stuck on the low stage: Two-stage furnaces run on low most of the time by design, which is quieter and more efficient but slower on very cold days.

What you can check yourself first

Before booking a service call, a few quick checks resolve a surprising number of slow-heating complaints:

• Replace the air filter if it looks grey or clogged. Most homes need this every 1 to 3 months, more often with pets or during wildfire smoke season.
• Walk the house and make sure supply and return vents are open and not blocked by rugs, furniture, or curtains.
• Confirm the thermostat is set to Heat and the schedule isn't holding a low temperature, and replace its batteries if it has them.
• Feel for cold drafts near windows and doors, and check that attic and crawlspace access hatches are closed.
• Give the system a full cycle. On a cold day, going from a deep setback to a comfortable temperature can genuinely take an hour or more.

If none of that changes anything, and the furnace runs almost non-stop without reaching your setting, the issue is likely inside the equipment or ductwork and worth a professional look.

When to call CANRO

Call a licensed technician if the furnace runs constantly but never satisfies the thermostat, if heating has gotten noticeably slower over one season, or if slow heating comes with short-cycling, odd smells, or unusual noises. These can point to a failing blower motor, a plugged heat exchanger, low airflow, or a control problem that needs proper diagnosis rather than guesswork.

CANRO Heating & Cooling is a licensed independent HVAC contractor serving Metro Vancouver since 1999, Red Seal certified and Technical Safety BC licensed (gas licence LGA0043870). We provide a diagnostic visit and a free written quote, so you know the real cause before spending on parts. If your furnace is aging and struggling, we can also walk you through replacement options and current CleanBC and FortisBC rebate programs, plus the federal Greener Homes Loan, that may apply. Call (604) 359-1081 or email info@canroheat.ca.

Frequently asked questions

Reviewed by the CANRO Heating & Cooling service team — July 07, 2026. Technical Safety BC gas licence LGA0043870 · boiler licence LBP0046450 · Red Seal certified · WorkSafeBC and liability insured · 4.9★ from 85+ Google reviews · serving Metro Vancouver since 1999 · (604) 359-1081.