How to Make Your House More Energy Efficient in Ontario’s Heat (2025 Guide)

It’s mid-August in Ontario, and the air feels like soup. Your AC has been running since breakfast, your upstairs bedroom is a sauna, and your utility bill just arrived with a number you’d rather not talk about. Sound familiar?

This summer 2025 heat is pushing Ontario’s homeowners— and their homes — to their limits. And while a brand-new air conditioner might seem like the obvious fix, experts agree that lasting comfort starts somewhere else entirely: making your home itself more efficient. That means keeping the cool air in, keeping the hot air out, and making your mechanical systems work smarter instead of harder.

We've put together a breakdown of where the biggest efficiency gains hide — and how to tackle them in a way that pays off, whether you’re renovating, building new, or just looking for strategic upgrades.

The Building Envelope - Where Efficiency Begins

Upgrading your air conditioner without first addresses leaks and inadequate insulation would be like upgrading the engine of a car that has 4 flat tires.

Think of your home’s “envelope” as the shell that separates indoor air from outdoor air — walls, windows, doors, roof, and floor. If that shell leaks like a sieve, no matter how big your A/C unit is, you're always going to be inefficient.

One of the simplest, most cost-effective steps you can take is air sealing. That means tracking down and sealing the little gaps and cracks that let conditioned air slip away: around window frames, under doors, through attic hatches, and even where pipes and wires enter the house. It’s unglamorous work — caulk guns, foam sealant, weatherstripping — but it’s one of the fastest ways to cut both cooling and heating bills.

Insulation is just as important. Many people have no idea that in Ontario, most older homes are under-insulated by today’s standards. The attic is usually the biggest opportunity for retrofitting because it is the easiest and most unintrusive space to access. Bringing your attic up to R-50 or R-60 — often by blowing in more loose-fill insulation — can make a dramatic difference in keeping summer heat out and winter heat in. Walls and floors matter too, especially if you have rooms over a garage or an unheated crawlspace or basement.

Windows and doors are another key part of the envelope. If replacements aren’t in the budget, weatherstripping, caulking, and storm windows or films can still help. If you are replacing, look for ENERGY STAR® products and pay attention to two numbers: U-factor (how well it insulates) and SHGC (how much solar heat it lets in). In our climate, a low SHGC can be your best friend in the summer, especially if you prefer to keep the blinds open and let lots of natural light in to your home.

HVAC Systems: Heat Pump or Traditional AC?

Once your home’s shell is in good shape, it’s time to think about the machinery that moves the air.

In recent years, cold-climate air-source heat pumps have become a serious alternative to the traditional furnace-plus-AC combo. Unlike older heat pumps that struggled in freezing weather, today’s models can heat efficiently in temperatures well below zero. In summer, they cool just as well as a high-end central air conditioner — sometimes better, thanks to variable-speed technology that can fine-tune output.

Heat pumps also pair beautifully with solar panels, since they run entirely on electricity. Geothermal (ground-source) heat pumps are even more efficient, though they come with a higher up-front price tag.

Whichever system you choose, proper sizing is critical. An oversized AC will cool the air too quickly without removing enough humidity, leaving the house clammy. An undersized unit will run constantly and still struggle on the hottest days. In Ontario, HVAC pros use a standard called CSA F280 to calculate the right size for your home based on insulation, windows, and orientation — not just square footage.

Community Voices: What Ontario Homeowners Are Experiencing

Heat pumps aren’t just a line in a government brochure — Ontario homeowners have been talking about their real-world performance in both summer and winter.

One homeowner shared that during a cold snap, when outdoor temperatures hit –13 °C, their home stayed at a steady and comfortable 21.5 °C indoors — without their backup heating system ever turning on. The secret? A well-sealed home with R-60 attic insulation and spray-foamed walls. (Reddit source)

Not every story is glowing, though. Another user found their hydro bill jumped to over $350 in January — up from $140 the year before — leading them to question the savings compared to natural gas. (Reddit source)

Others report a middle ground: in Hamilton, one homeowner with a hybrid heat pump and furnace setup noticed their home became comfortable more quickly, stayed evenly heated, and even ran quieter — with lower bills to boot. (Reddit source)

And for those building new, some say a heat pump is a “no-brainer,” especially when combining heating and cooling into a single system. Still, others note that in areas with cheap natural gas, you’ll want a heat pump with a high seasonal efficiency (COP of 4 or more) to come out ahead. (Reddit source)

The takeaway? Heat pumps can deliver excellent year-round comfort, but their success depends on good design, tight insulation, and the economics of your local utility rates.

Air Distribution: Where the Air Goes Matters

Even the best HVAC system can’t work properly if the air isn’t getting where it needs to go.

Supply registers — the vents where air comes out — should be placed to counteract the biggest heat gains, often near exterior walls or large windows. Return vents — where air goes back to be cooled or heated again — need to be strategically located so air can circulate freely through each level of the house.

Ontario’s building code requires at least one return-air inlet per floor, but a well-designed system will often have more. Renovations are a perfect time to add returns or rebalance ductwork for better comfort.

When Air Meets Aesthetics: Seamless Integration in Oakville

In some homes, registers and returns are purely functional. But in one of our recent custom home projects in Oakville, we proved they can be a design feature in their own right.

Instead of standard grilles and protruding baseboards, this home uses flush-mounted, integrated trim and vent systems. The baseboards are built right into the drywall for a sleek, minimalist profile. Return air vents are concealed within the wall surface, creating a perfectly flush look. Even the floor registers disappear seamlessly into hardwood and tile, maintaining a clean, contemporary aesthetic.

It’s a perfect example of how air distribution doesn’t have to compromise style. With thoughtful planning, the elements that make your home comfortable can also make it beautiful.

Keep Your Attic Cool and Dry

A hot, stagnant attic makes your cooling system work harder — and can actually damage your roof structure over time through mold, mildew and rot. That’s why proper attic ventilation is non-negotiable.

Good ventilation is a balance of intake (soffit vents under the eaves) and exhaust (ridge or roof vents). The goal is to draw cooler outside air in at the bottom and push hot, moist air out at the top. In Ontario, the general rule is about one square foot of net free vent area for every 300 square feet of insulated ceiling — or one per 150 for low-slope roofs.

If you’re adding insulation, it's important to not forget baffles in order to keep soffit vents from being blocked.

Light, Heat, and the Hidden Energy Load

Sometimes, the heat is coming from inside the house — literally.

Traditional incandescent bulbs turn about 90% of the energy they use into heat, not light. Swapping to LEDs reduces that waste, cuts your electricity bill, and lightens the load on your AC. The same logic applies to appliances and electronics. A large plasma TV or an old dehumidifier might be quietly adding unwanted heat to your home. These little changes are small, but they do all add up, especially in smaller rooms.

Ceiling fans are another low-tech but high-impact tool. They don’t actually cool the air, but they make you feel cooler, which means you can nudge the thermostat up a degree or two without losing comfort.

Find the Weak Spots Before You Spend Big

Guessing at where your home loses energy is risky — and often wrong. That’s why energy advisors recommend a blower-door test as part of an EnerGuide home evaluation. This test uses a powerful fan to pressurize your home and reveal exactly where the leaks are.

Common culprits include attic hatches, rim joists, recessed lights, and rooms over garages. Once you know the trouble spots, you can target your upgrades for maximum impact.

The 2025 Ontario Incentive Landscape

If you’re thinking about efficiency upgrades this year, there’s good news: Ontario’s new Home Renovation Savings Program, co-delivered by Save on Energy and Enbridge Gas, launched in January 2025. It offers rebates for insulation, heat pumps, smart thermostats, and more.

Other programs, like the Home Efficiency Rebate Plus and Canada Greener Homes Grant, are in their final year — both require post-retrofit work and paperwork to be wrapped up by the end of 2025. That means if you want to take advantage, you’ll need to move quickly. Contact us for more information.

The Bottom Line

Making your house more energy efficient isn’t just about keeping cool in August — it’s about comfort, lower bills, and resilience in every season. Whether you’re sealing leaks, upgrading insulation, or swapping out your HVAC system, the key is to think of your home as a whole system.

And if you’re not sure where to start? Test first, plan second, and then invest in the upgrades that will give you the most bang for your buck.

Frequently Asked Questions:

What is the most cost-effective way to make my house more energy efficient?

In most Ontario homes, air sealing and adding insulation offer the fastest return on investment. Sealing drafts around windows, doors, and attic hatches, then topping up attic insulation to R-50 or higher, can significantly reduce both heating and cooling costs.

Are heat pumps worth it in Ontario’s climate?

Yes — modern cold-climate heat pumps are designed to operate efficiently well below freezing. They can heat in winter, cool in summer, and often replace both a furnace and an air conditioner. They work especially well when paired with solar panels.

How do I know if my air conditioner is the right size for my home?

In Ontario, proper sizing is calculated using the CSA F280 standard, which considers insulation, windows, and home layout — not just square footage. An oversized system will short-cycle and leave the air humid; an undersized unit will run constantly but never catch up.

What are flush-mounted vents and why would I want them?

Flush-mounted vents are integrated directly into walls, floors, or ceilings for a seamless look. They blend with finishes like drywall, hardwood, or tile, creating a clean, modern aesthetic without sacrificing airflow. They were featured in Imperio’s Oakville custom home project.

Are there rebates for energy efficiency upgrades in Ontario?

Yes. In 2025, the new Home Renovation Savings Program (Save on Energy + Enbridge Gas) offers rebates on insulation, heat pumps, and more. Other programs, like Home Efficiency Rebate Plus and Canada Greener Homes Grant, are wrapping up this year and have firm deadlines.