Many Ontario homes — particularly brick and frame construction built between 1940 and 1980 — have empty or poorly-filled wall cavities that are silently driving up heating bills. Retrofit wall insulation doesn't require tearing down your walls, but it does require getting the diagnosis right first.
The answer depends entirely on what's already in your walls. Thermal imaging during a certified energy audit will show whether your wall cavities are empty, partially filled, or already insulated. Before recommending any wall insulation work, we need that baseline picture.
For older Toronto, Hamilton, and inner-GTA brick homes with empty cavities, wall insulation retrofits frequently offer payback periods under 10 years — competitive with attic work in many cases. For homes with full stud cavities already, the marginal return is much lower and the money is usually better spent elsewhere in the envelope.
Drill-and-fill (blown-in dense pack): Small holes are drilled through the exterior cladding or interior plaster, and cellulose or fibreglass is blown in under controlled pressure to fill the cavity. Works well for standard framed walls. Less expensive than injection foam. Can have voids if framing details are irregular.
Injection foam: A low-density, water-based foam is injected through small holes and expands to fill irregular cavities. Excels in older homes with lath-and-plaster construction and complex framing. Slightly higher cost but often better cavity fill in difficult conditions.
Exterior continuous insulation: The highest-performance solution, but requires replacing siding. Best suited to homes already planning exterior cladding replacement. See related guidance on our insulation overview page.
Costs depend heavily on home size, wall construction, access conditions, and chosen method. Rough ranges for a typical GTA detached home:
Rebate eligibility under the HRS Program can significantly offset these costs — particularly when wall insulation is combined with attic and air sealing work as part of a whole-home retrofit package.
For homes where the budget requires prioritizing, our advisory process will tell you whether wall insulation or another measure delivers better value for your specific home. See also how air sealing and wall insulation interact.
A certified audit with thermal imaging tells you exactly what you're dealing with — and whether wall insulation belongs at the top of your list.
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