If you've had an insulation quote, you've probably heard the term "R-value" thrown around without much explanation. It's the single most useful number for understanding whether your attic is actually doing its job — so here's what it means and what it means for your home.
What R-value actually measures
R-value measures a material's resistance to heat flow. The higher the number, the better that layer of insulation slows heat from escaping in winter and entering in summer. It's cumulative — if you add insulation on top of what's already there, the R-values stack.
What R-value does not tell you is air-tightness. A well-insulated attic that's full of air leaks (around pot lights, plumbing stacks, the attic hatch) will still lose heat, which is why insulation upgrades are usually paired with air sealing.
What's typical in older Toronto-area homes
Many homes built before the 2000s in Toronto and the GTA were insulated to standards that are well below what's recommended today — often in the R-12 to R-25 range in the attic, sometimes less if insulation has settled or been disturbed over the years (a common issue with older blown-in fibreglass or cellulose).
The recommended target
For most homes in this climate zone, the recommended attic insulation level is R-50 to R-60. That's a significant jump from what a lot of older attics are currently sitting at — which is also why attic insulation upgrades tend to be one of the highest-value projects a homeowner can do, both for comfort and for rebate eligibility (see our Ontario rebates page for current amounts).
How to find out where you stand
Short of climbing into your own attic with a tape measure, the most reliable way to know your current R-value is to have it assessed. During a free estimate, we measure your existing insulation depth and material type, and tell you exactly where you land relative to the recommended target — no guesswork.