Ontario Homeowner's Guide to Summer Insulation 2026
May 29, 2026
Summer 2026 is fast approaching, and we’re getting ahead of it with Great Northern Insulation’s guide to summer insulation. Whether you’re considering making use of the excellent rebate programs currently available for improved attic insulation, wondering how to make temperatures within your home more consistent between floors, or just looking to decrease your cooling costs, this guide is for you.
Why Insulation Matters in the Summer
Most people think of insulation as something only beneficial in the winter. However, the same insulation that helps keep heat inside in January also helps keep heat outside in July.
In the summer, a well-insulated home resists heat entering through the attic, walls, and basement, which means your air conditioning system – whether it’s whole-home HVAC, a window unit, or a portable AC unit – doesn't have to work as hard to maintain a comfortable temperature indoors. This not only means that temperatures stay more consistent indoors, but it also means you’ll be spending less on hydro bills during the hottest months of the year.
If you don’t have air conditioning, improved insulation still helps slow the transfer of heat into your home, keeping it cooler for longer. If you’re a cottage owner, insulation helps to manage indoor humidity levels, a common source of the musty smell that tends to fill a cottage after you’ve been gone for a few days. Finally, insulation also helps extend the lifespan of building materials, as excessive heat can damage structural wood and drywall.
Signs Your Home Needs Better Insulation
If any of these sound familiar, it might be time to get in touch with Great Northern Insulation.
- Upstairs floors are noticeably hotter than the rest of the home.
- Your AC runs constantly but the house doesn’t hit target temperatures.
- Hydro bills spike when the air conditioning turns on in the summer.
- Temperatures vary from room to room.
- Your cottage feels humid or musty when you arrive.
Not every issue here is necessarily directly caused by poor insulation, but these are some of the most common pain points our customers tell us about. If they describe your home or cottage, a free quote from Great Northern Insulation is a smart next step.
The Best Areas to Insulate
Your entire home’s insulation and air sealing works as a system called your home’s thermal envelope. If insulation is lacking in one area, that weak point can impact your whole home’s comfort. Here are some of the most popular areas of the home that Great Northern Insulation customers target in the summer months:
Attic
You probably saw this one coming – the attic is where the biggest gains are for most homes, and the least invasive option for home insulation upgrades. If your home was built prior to 2010, your attic space is likely currently below the R-50 to R-60 current Ontario Building Code requirements in Ontario and would probably benefit from a top-up.
Basement and Rim Joists
If you’ve ever read an article by Great Northern Insulation about the most overlooked areas of the home for insulation, you’ve probably heard us speak about rim joists. It’s the area of your basement where the basement wall meets the upper-level floor, and it’s often under-insulated or missing insulation entirely. This area of the home is above grade, meaning it can be a huge source of air leakage and heat transfer.
Crawlspaces
Like basement insulation, crawl spaces are often under-insulated and can allow unconditioned, humid air to enter the home from below. Spray foam is one of the most popular choices for crawl space insulation among Great Northern Insulation’s customers.
Cottages
For cottages, seasonal properties, and areas with irregular construction, framing, and other gaps, spray foam insulation is often the best solution for a solid seal and insulative value. It expands to fill voids completely, provides an air and vapour barrier, and won’t rot or gather mildew over time.
Why Summer Is A Great Time To Insulate
Here’s three big reasons why Summer 2026 is a great time to insulate:
- You'll see the benefits immediately. Better insulation improves indoor temperatures and the effectiveness of your air conditioning right now, and that comfort and cost savings will continue into the cooler months.
- You’ll beat the more crowded months for home insulation upgrades. Many people incorrectly consider improved insulation to only be beneficial in the winter months, meaning Great Northern Insulation’s busiest time of year is in the fall and winter seasons. By completing upgrades earlier, you’ll have more scheduling flexibility.
- Finally, the Home Renovation Savings program attic stream means that this is the best time in years to upgrade your attic insulation. Rebate amounts were increased in January 2026, making an already great rebate program even better.
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Ontario’s HRS Attic Stream Rebate – What You Should Know
Ontario homeowners can receive up to $1,250 in rebates for standard attic insulation upgrades through the Home Renovation Saving Program’s standalone attic stream – with no upfront energy assessment required. Cathedral ceiling upgrades are eligible for up to $750.
Great Northern Insulation is a participating contractor and handles the full application process on your behalf. You provide us with the necessary information and your signed form, and we take it from there.
The program is currently scheduled to run through November 2026, but rebates are available on a first-come, first-served basis and the program terms and conditions state that it can be closed at any time.
Learn more about the standalone attic rebate here.
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Ready to Get Started?
Great Northern Insulation’s quotes are always free, with no obligation. Our experts can help you understand your home’s current insulation levels, identify highest-impact upgrades, and guide you through current rebate programs to maximize cost savings – all before you commit to anything.
We’ve been Ontario’s most trusted insulation provider for more than 45 years, with thousands of 5-star reviews across Google, Homestars, and other review platforms.
Get in touch today for a free assessment from Great Northern Insulation!
Frequently Asked Questions – Insulation and the Summer
Why is my upstairs so hot in the summer?
Two big reasons: first, warm air naturally rises and tends to collect upstairs. Second, your upper floors sit directly under the attic and roof, which can get extremely hot in the summer sunlight. Without proper insulation and air sealing, this heat transfers into the rooms below. Improving attic insulation and sealing air leakage helps reduce heat transfer into your living spaces.
Does attic insulation help in the summer?
Yes, absolutely. Attic insulation slows the transfer of heat, which works in both directions – slowing heat from entering your home in the summer, and slowing heat from escaping in the winter.
Can insulation lower my air conditioning costs?
It can, yes, as part of a properly-functioning home envelope. When your home is properly insulated and sealed, your HVAC systems don’t need to run as frequently or for as long to maintain a comfortable temperature. Actual cooling cost savings depend on many factors, including your home’s age, location, level of shade, and more, but improving your insulation and air sealing can often have an impact on your heating and cooling costs.
What insulation is best for Ontario cottages?
It depends on the cottage, which is why Great Northern Insulation offers no-obligation quotes and access to our knowledgeable experts. However, spray foam insulation is an extremely popular choice for our customers’ cottages, especially for crawl spaces. It provides an air and vapour barrier, great insulative value, and seals gaps and cracks.
Should I insulate my cottage if it’s only used seasonally?
Insulating and air sealing seasonal properties can help protect it year-round by helping to prevent conditions that can lead to mold and mildew and i. For cottage owners looking to turn a seasonal cottage into one usable year-round, insulation and air sealing are even more important.
How do I know if my home needs more insulation?
Start with the signs listed earlier in this article or give our experts a call at 1-800-265-1914 if you’re unsure. You can also do a basic self-assessment for most areas of the home: if you can access your attic hatch safely, you can check your attic insulation for signs of damage or degradation, and gauge general depth. If you can see your attic ceiling joists, for example, that means your attic is very low on insulation!
What areas of a home lose the most cool air?
Thermal energy transfer happens in one direction – from an area of higher temperature (such as your attic space or roof) to an area of lower temperature (the cooler indoor spaces). Your attic is usually the biggest factor in summer heat entering a home, which is why attic insulation is so effective at slowing down and mitigating that heat transfer. Air leakage around windows, doors, electrical penetrations, and plumbing stacks are also big contributors to an uncomfortable home in the summer.
Is summer a good time to upgrade insulation?
Yes, absolutely! It’s one of the best times. Installation conditions are ideal, scheduling is easier than in the fall rush, and you’ll benefit from the upgrade immediately during peak cooling season.
How long do insulation installs or upgrades take?
Most residential insulation upgrades are completed in a single day. Great Northern Insulation’s professional install teams can complete multiple attic upgrades in a single day for an average-sized home. The actual timeline depends on the scopes of work being completed and the size of your home. A Great Northern Insulation consultant can give you a specific estimate as part of your free quote.
Is spray foam insulation worth it in Ontario?
Spray foam insulation is one of Great Northern Insulation’s most popular products. It provides superior insulative value alongside an air and vapour barrier and expands to fill gaps that batt or blown-in insulation can’t. It’s perfect for rim joists, crawl spaces, and anywhere else a complete air and moisture barrier matters most. Spray foam insulation does cost more than other insulation types, which is why Great Northern Insulation’s consultants will recommend it where it’s genuinely the best product for the scope of work, or will recommend spray foam insulation in conjunction with other insulation types as a dual-system install that balances the best possible insulation products and cost savings.
