The first cold snap in Ontario has a way of exposing every weak spot in a house: the bedroom that never warms up, the furnace that runs nonstop, the draft you can feel from the couch. Most of those problems are cheaper and easier to fix in October and November than in the middle of January, when HVAC companies are booked solid and you are already paying for the heat you’re losing.
This winter home checklist walks through what to check before the deep cold arrives, starting with your heating system, then your safety equipment, then the building itself, from the attic down to the basement. Some items take five minutes. A few are jobs for a pro. Work through them in order and you’ll go into winter with a warmer, safer, more efficient home.
1. Book a Furnace or Heat Pump Tune-Up Before the Rush
Your heating system is the heart of winter comfort, and it’s the one thing you really don’t want to fail during a cold snap. A licensed HVAC technician should inspect it once a year, ideally in early fall. A typical tune-up includes checking the burner and heat exchanger, testing safety controls, inspecting the blower and electrical connections, and confirming the system is venting properly.
The Canadian Gas Association points out that the weeks before heating season are the best window for furnace maintenance, and that your local gas utility is a good starting point if you need to find service.
Signs your system needs attention now:
- Some rooms are much colder than others
- The furnace short-cycles (turns on and off frequently) or runs almost constantly
- Unusual noises: banging, rattling or squealing
- A yellow or flickering burner flame on a gas furnace (it should be steady and blue)
- Your heating bill jumped compared to last winter with no change in usage
One important note: if certain rooms stay cold even after a tune-up, the furnace may not be the problem. Cold rooms over garages, above unheated crawl spaces or directly under the attic are often losing heat through the building itself. More on that below.
2. Replace the Furnace Filter (and Set a Reminder)
A clogged filter forces your furnace to work harder to push air through the ducts, which costs you money and adds wear to the blower. Standard 1-inch filters generally need replacing every one to three months during heating season, and more often if you have pets, allergies or ongoing renovation dust. Thicker media filters last longer, so check the manufacturer’s recommendation for yours.
Buy a few filters now so you’re not making a hardware store run in a snowstorm, and put a recurring reminder in your phone.
3. Clear Furnace Vents, Intakes and Registers
Most newer high-efficiency furnaces vent through plastic pipes on the side of the house. If snow or ice blocks the intake or exhaust, the furnace can shut itself off. After every major snowfall, clear the area around those pipes.
Inside, walk the house and make sure supply registers and return-air grilles aren’t blocked by furniture, rugs or curtains. Blocked returns are a surprisingly common cause of uneven heating.
4. Test Your Carbon Monoxide and Smoke Alarms
Winter is when furnaces, fireplaces and water heaters run hardest, which makes it peak season for carbon monoxide risk. Ontario’s rules got stricter this year: as of January 1, 2026, homes with a fuel-burning appliance, a fireplace or an attached garage need CO alarms on every storey, in addition to alarms next to all sleeping areas. You can read the details on the Government of Ontario’s carbon monoxide safety page.
- Press the test button on every smoke and CO alarm
- Replace batteries if your alarms aren’t hardwired or sealed-battery units
- Check the manufacture date. CO alarms wear out and need to be replaced as a whole unit, usually after 7 to 10 years (check your model’s instructions)
- Make sure there’s a CO alarm on every level of the home, including the basement
5. Get Your Thermostat Working for You
A programmable or smart thermostat lets you lower the temperature while you’re asleep or out of the house without coming home to a cold living room. If you already have one, confirm the schedule still matches your routine and that it’s switched from cooling to heating mode. If you have a heat pump, follow the manufacturer’s guidance on setbacks, since large temperature swings can trigger less efficient backup heat on some systems.
Also, look at where your thermostat is mounted. If it sits near a drafty door, in direct sun or next to a heat register, it will misread the room and your whole house will feel off.
6. Check Your Attic Insulation
Your attic is one of the biggest places heat escapes. Warm air rises, and if the insulation above your ceiling is thin, compressed or patchy, that heat goes straight into the attic and out through the roof. In many older GTA homes, the original attic insulation is well below what’s recommended today.
How to do a quick check yourself:
- Look at the joists. Pop open the attic hatch (safely, with a flashlight) and look across the attic floor. If you can see the tops of the wooden ceiling joists, you almost certainly don’t have enough insulation.
- Look for uneven coverage. Bare patches, low spots and areas where insulation has been pushed aside by past electrical or HVAC work all leak heat.
- Look for damage. Insulation that’s damp, matted, stained, or full of rodent droppings has lost much of its value and may need to come out before new insulation goes in. Our attic insulation removal service handles this safely.
- Watch for old vermiculite. Loose, pebble-like insulation that’s grey-brown or gold may be vermiculite, which can contain asbestos. Don’t disturb it. Have it assessed by a professional first.
If your attic needs a top-up, blown-in insulation is the most common solution for Ontario homes. Both blown-in fiberglass and blown-in cellulose fill around joists, wires and other obstructions far better than rolls of batts in an existing attic. Learn more on our attic insulation services page.
Don’t Forget Ventilation and Air Sealing
More insulation alone isn’t the whole job. Natural Resources Canada’s homeowner guide, Keeping the Heat In, treats air leakage control as a core part of any energy upgrade. In the attic, that means:
- Sealing gaps around pot lights, plumbing stacks, wiring holes and the top plates of interior walls, so warm, moist air from the house can’t leak into the attic
- Keeping soffit vents open. Insulation should never block the airflow coming in at the eaves. Baffles hold insulation back so the attic can breathe
- Making sure bathroom and kitchen fans vent outside, not into the attic
7. Seal and Insulate the Attic Hatch
The attic hatch is often the single leakiest spot on the top floor: a thin piece of drywall or plywood with no insulation and no seal. Add weatherstripping around the frame and attach a piece of rigid foam insulation to the top of the hatch. It’s an inexpensive fix that makes a noticeable difference.
8. Watch for Ice Dams and Attic Frost
Ice dams, the thick ridges of ice along the edge of the roof, usually form when heat escapes into the attic, warms the roof deck and melts the snow above it. That water runs down, refreezes at the colder eaves, and can back up under shingles.
Large icicles, ice buildup at the gutters, or frost on the underside of the roof sheathing in the attic are all signs that warm, moist air is getting into the attic. The fix is usually a combination of air sealing, proper insulation depth and clear ventilation, not just roof heating cables.
9. Stop Drafts at Windows and Doors
On a windy day, hold the back of your hand (or a lit incense stick) near window frames, door frames, baseboards and electrical outlets on exterior walls. Anywhere you feel air moving, you’re losing heat.
- Replace worn or flattened weatherstripping on exterior doors
- Add a door sweep if you can see daylight under the door
- Re-caulk cracked or gapped trim around windows
- Install foam gaskets behind outlet and switch covers on exterior walls
- Use heavy curtains at night on older single-pane or poorly sealed windows
These are easy DIY jobs. If your house still feels drafty after you’ve done them, the leaks are probably somewhere you can’t see, inside walls, around the foundation or in the attic. Whole-home air sealing systems like AeroBarrier are designed to seal those hidden gaps.
10. Fix the Cold Room Over the Garage
If you have a bedroom or bonus room above an attached garage, you probably already know it’s the coldest room in the house. The floor of that room is the ceiling of an unheated garage, and it’s often poorly insulated or has gaps around the rim joists. Garage ceiling insulation, often with spray foam to seal the tricky edges, is the most common fix.
Keeping the garage door closed as much as possible also helps, and is important for carbon monoxide safety if you ever idle a car in there (which you shouldn’t).
11. Check the Basement Rim Joists and Exposed Ducts
Head to the basement and look at the top of the foundation wall, where the wooden floor framing sits on the concrete. This area, called the rim joist or header, is one of the leakiest spots in many Ontario homes. If it’s bare wood or has loose batts stuffed in, cold air is getting in. Spray foam is well suited here because it insulates and air seals in one step.
While you’re down there, look at any ductwork running through unheated spaces such as a crawl space or garage. Duct joints that are disconnected or leaking push heated air into spaces you aren’t trying to heat. Sealing duct joints with foil tape or mastic (not regular cloth duct tape) is something your HVAC technician can handle during a tune-up.
12. Protect Your Plumbing
- Shut off the interior valve that feeds outdoor hose bibs, then open the outside tap to drain it
- Disconnect and store garden hoses
- Insulate exposed water pipes in unheated areas such as garages, crawl spaces and along exterior walls
- Know where your main water shut-off is, in case a pipe does burst
13. Clean Gutters and Check the Roof
Once the leaves have finished falling, clean out the gutters and make sure downspouts carry water away from the foundation. Clogged gutters make ice dams worse. From the ground, scan the roof for missing or lifted shingles and damaged flashing around the chimney and vents, and get them repaired before snow covers them.
14. Manage Indoor Humidity
Winter air tends to be dry, but too much humidity is also a problem. Heavy condensation or frost on the inside of windows is a sign the indoor air is too moist for the outdoor temperature, and that moisture can also be finding its way into your walls and attic. Run bathroom fans during and after showers, use the range hood when cooking, and if you use a humidifier, turn it down as outdoor temperatures drop.
15. Prepare for Power Outages
Ice storms and winter windstorms can knock out power, and with it, your furnace. Keep flashlights, batteries, blankets, bottled water and a battery-powered phone charger where you can find them in the dark. Never run a generator, barbecue or fuel-burning heater inside the house or in an attached garage.
Your Quick Winter Home Checklist
| Task | DIY or Pro? | When |
|---|---|---|
| Furnace or heat pump tune-up | Pro | Early fall |
| Replace furnace filter | DIY | Every 1–3 months |
| Clear furnace vents and registers | DIY | After each snowfall |
| Test smoke and CO alarms | DIY | Fall, then monthly |
| Set thermostat schedule | DIY | Start of heating season |
| Check attic insulation depth | DIY check, pro install | Before winter |
| Seal attic hatch | DIY | Before winter |
| Weatherstrip doors and caulk windows | DIY | Fall |
| Insulate garage ceiling or rim joists | Pro | Fall |
| Shut off and drain outdoor taps | DIY | Before first hard frost |
| Clean gutters | DIY or pro | Late fall |
| Build an outage kit | DIY | Before winter |
Can You Get a Rebate for Attic Insulation in Ontario?
Possibly. The Home Renovation Savings program, offered by Enbridge Gas and Save on Energy, has included rebates for homeowners who upgrade their attic insulation to at least R-50, including a standalone attic option that doesn’t require a full home energy assessment. Eligibility depends on your current insulation level and other program rules, and like any rebate program, terms and deadlines can change or the program can close with little notice.
See our Home Renovation Savings rebate page for how the process works, and check the official program site at homerenovationsavings.ca for current terms.
Frequently Asked Questions
When is the best time to add attic insulation?
Any time of year works, since blown-in insulation is installed from inside the attic and isn’t affected by weather. Fall is popular because you start saving on heating right away, but winter installs are common too.
How do I know if my house is losing heat through the attic?
Common signs include cold upstairs rooms, high heating bills, uneven snow melt on your roof compared to neighbours’ homes, large icicles or ice dams, and visible ceiling joists in the attic.
Should I fix my furnace or my insulation first?
Make sure your furnace is safe and working first, since that’s a safety issue. After that, improving insulation and air sealing reduces how hard the furnace has to work. If you’re planning to replace your heating system, upgrading insulation first can also mean you need a smaller, less expensive unit. Ask your HVAC contractor about sizing.
How often should I change my furnace filter in winter?
For a standard 1-inch filter, every one to three months is a common guideline. Check it monthly during heating season and replace it when it looks grey or dusty.
Have more questions? Visit our insulation FAQ or browse more home comfort guides.
Get Your Home Ready Before the Deep Freeze
A tuned-up furnace and a well-sealed, well-insulated house work together. One produces the heat; the other keeps it inside. If your attic needs a closer look, or you’ve got a cold room you can’t seem to fix, Pro Insulation Contracting can inspect your home and tell you what it actually needs.
We serve homeowners across the GTA, including Toronto, Vaughan, Markham, Richmond Hill and North York.
Book your free inspection or call (416) 315-0471.