You can hear it from the basement: the furnace kicks on, runs, shuts off, and kicks on again. Or it barely stops at all on the coldest nights. Meanwhile, the house still doesn’t feel warm. If that sounds like your Mississauga home, the problem probably isn’t the furnace. It’s what happens to the heat after the furnace makes it.
Here’s how to keep your home warmer this winter and give your heating system an easier job.
Long Run Times Usually Mean Heat Loss
A furnace that runs for very long stretches is usually keeping up with a house that loses heat quickly. That’s common in Mississauga’s many 1970s and 1980s subdivisions, in neighbourhoods like Erin Mills, Meadowvale and Applewood, where homes were built to the insulation standards of the time and the attic insulation has had decades to settle.
Before you assume the furnace needs replacing, it’s worth looking at the house it’s heating. A furnace that’s a good match for a well-insulated home can look undersized in a leaky one.
Check the Easy Things First
- Furnace filter: A clogged filter restricts airflow and makes the blower work harder. Check it monthly in winter.
- Registers and returns: Make sure furniture, rugs and curtains aren’t blocking them.
- Thermostat placement: A thermostat near a drafty door or in direct sun can give false readings.
- Annual service: If it’s been more than a year, book a technician.
If those all check out and the furnace is still running long, the house is the next place to look.
The Attic: Where Most of the Fix Is
Heat rises, so a thin attic means the heat you paid for is drifting straight through your ceiling. Attic insulation in Mississauga is typically the upgrade that shortens furnace cycles the most, because it reduces the heat loss the furnace is constantly fighting.
What a Properly Insulated Attic Looks Like
Ontario’s attic rebate program targets R-50. That’s about 13 to 15 inches of blown-in cellulose or 17 to 19 inches of blown-in fibreglass, spread evenly with no joists showing. Many older Mississauga attics have half of that or less.
The work is usually a top-up over existing insulation, as long as it’s clean and dry. If it isn’t, attic insulation removal comes first. Either way, baffles at the eaves keep your soffit vents open so the attic stays dry.
Seal the Leaks the Furnace Can’t Outrun
Air leaks matter as much as insulation. Gaps around pot lights, exhaust fans, plumbing stacks and the attic hatch let warm air escape continuously. Every cubic foot that leaks out is replaced by cold outside air the furnace has to heat. AeroBarrier air sealing seals the whole house from the inside, and weatherstripping the attic hatch is a quick DIY start.
Other Places to Look
- Rim joists: 2 lb closed-cell spray foam stops cold air entering at the top of the foundation.
- Room over the garage: Garage ceiling insulation warms the floor from below.
- Exterior doors: Replace worn weatherstripping and add door sweeps.
Rebates for Mississauga Homeowners
The Home Renovation Savings program offers up to $1,250 for bringing an attic up to R-50 with no energy assessment, as long as the work is done by a participating contractor. Detached homes, semis and row townhouses qualify; stacked townhouses don’t. Gas-heated homes must be Enbridge Gas customers. There’s also a smart thermostat rebate. The program runs to November 30, 2026, unless it changes. See our energy rebate page for details.
Frequently Asked Questions
Is it normal for my furnace to run constantly when it’s very cold?
On the coldest nights, longer run times are normal. But if it runs nonstop in moderate weather, or the house never reaches the set temperature, your home is likely losing heat faster than it should.
Should I replace my furnace or insulate first?
Insulate and air seal first in most cases. Reducing heat loss can change what size of furnace your home actually needs, so it’s smart to do before any replacement.
How long does attic insulation take?
Most attic top-ups take a day or less, and you can stay home throughout.
Give Your Mississauga Furnace a Break
Pro Insulation Contracting will measure your attic, check for leaks and show you what will actually make a difference. Book a free assessment or call (416) 315-0471.
