Every September, Toronto homeowners get the same rude surprise: that first cold morning when the thermostat calls for heat and nothing happens. Furnace won't ignite. Vents blow cold. Somewhere a pipe is already freezing because the insulation got pulled out during a summer reno. This checklist covers everything you need to do before winter arrives — or, if you're reading this in January with a broken furnace, what to do right now. Bookmark this. You'll need it every year.
[IMAGE: A homeowner changing their furnace filter before winter — alt: Toronto homeowner replacing a dirty furnace filter during fall winter preparation in a residential basement]
When should I schedule my furnace tune-up before winter?
Book it in September or early October. HVAC companies in the GTA get absolutely slammed after the first cold snap — wait until mid-November and you'll be on a two-week waitlist while your family shivers in parkas. A fall furnace tune-up includes cleaning or replacing the air filter, testing the igniter and flame sensor, measuring gas pressure, inspecting the heat exchanger for cracks, checking the blower motor and belt, and running a combustion analysis to verify efficiency and CO levels.
If your furnace is more than 15 years old, ask the technician to do a heat exchanger inspection with a borescope camera. A cracked heat exchanger leaks carbon monoxide into your ductwork — it's the single most dangerous furnace failure. [link to: HVAC Services page]
How do I stop my pipes from freezing in a Toronto winter?
Pipes in unheated basements, crawl spaces, and exterior walls freeze when temperatures drop below -10°C — which happens multiple times every Toronto winter. The three things that prevent frozen pipes: insulation (foam pipe sleeves on all exposed copper and PEX), heat (keep the basement above 12°C even if you're away), and airflow (open cabinet doors under kitchen and bathroom sinks on exterior walls during cold snaps to let warm room air reach the pipes).
Drain and shut off outdoor hose bibs before the first freeze. Disconnect your garden hose. If you have an interior shutoff valve for each outdoor tap, close it and open the outdoor valve to let residual water drain. Frozen hose bibs crack and flood basements when they thaw in spring — this is one of the most common preventable insurance claims in Markham and Richmond Hill where larger lots mean longer pipe runs to outdoor taps.
[IMAGE: Foam pipe insulation being installed on exposed copper pipes — alt: Installing foam pipe insulation on exposed copper water pipes in a Toronto basement to prevent freezing]
What temperature should I set my thermostat to in winter?
21°C (70°F) during the day when you're home, 17-18°C (63-64°F) at night or when you're away. Every degree you lower your thermostat for 8+ hours saves about 2% on your heating bill. A programmable or smart thermostat pays for itself in one winter. For condos and townhouses in Vaughan and Newmarket, where shared walls reduce heat loss, you can typically set back 3-4°C without noticing a comfort difference.
Should I cover my outdoor AC unit in winter?
Only with a breathable cover — never with plastic sheeting or an impermeable tarp that traps moisture and rusts the condenser coil. Modern AC units are designed to sit outside year-round in snow and ice. The real risk is not snow but falling ice from your roof or gutters. If your AC is directly under an eave without gutters, install a plywood shield or a purpose-made condenser cover that has ventilation panels.
Don't run your AC when outdoor temperatures are below 10°C — the compressor oil thickens and you can damage the unit. If your home gets stuffy on mild winter days, open a window for a few minutes rather than running the cooling cycle.
What's the best filter for a furnace in winter?
Use a MERV 8 filter and change it every 60-90 days during heating season — more often if you have pets or allergies. Don't use MERV 13 or HEPA-grade filters in a standard 1" filter slot. They're too restrictive for most residential blowers, reducing airflow, increasing static pressure, and making your furnace work harder for less heat output. If you need better filtration (allergies, asthma), have an HVAC tech install a 4" or 5" media cabinet — it gives you MERV 11-13 filtration with the same airflow resistance as a 1" MERV 8.
Is my fireplace or gas insert safe to use as backup heat?
If you have a wood-burning fireplace, have the chimney swept and inspected annually before burning season. Creosote buildup causes chimney fires, and Toronto Fire Services responds to dozens of these every winter. Gas fireplaces and inserts also need annual service — the thermocouple, pilot assembly, and burner should be cleaned and tested. And never use a gas stove or oven as a heat source during a power outage, even if your furnace is down. It's a carbon monoxide risk and a fire hazard.
Frequently Asked Questions
Replace the air filter, vacuum around the furnace and inside the burner compartment (carefully), test the thermostat by raising the set point 5°C to confirm the furnace fires, check that all supply vents are open and not blocked by furniture, and verify your CO detector has fresh batteries. Anything beyond these basic steps — especially opening the furnace cabinet — should be left to a licensed technician.
Ontario law requires a CO detector outside every sleeping area. Best practice is one per floor, including the basement if you have a furnace, water heater, or gas dryer down there. Test them monthly and replace batteries when you change clocks for daylight saving. CO detectors expire after 7-10 years — check the manufacture date stamped on the back.
Running the fan continuously (the "ON" position rather than "AUTO") evens out temperatures between floors and improves filtration, but it adds $30-$50/month to your electricity bill and wears out the blower motor faster. The best compromise: use a smart thermostat's "circulate" mode, which runs the fan 15-20 minutes per hour regardless of heating calls. You get most of the air-mixing benefit without the energy penalty.
Winter-Ready Starts Here. Book Your Furnace Tune-Up.
Furnace inspections, pipe insulation checks, and full HVAC winter prep across Toronto, Etobicoke, Mississauga, Vaughan, Richmond Hill, Markham, and Newmarket. $150 fee waived when you approve the work.
Internal Links: [link to: HVAC Services page] · [link to: Furnace Installation page] · [link to: Maintenance Plan page]