R-60 is the current target for attic insulation in new Ontario construction and the upper end of what most retrofit programs aim for. If you're reading about R-values and wondering whether you need R-60 specifically, here's what the number means and what the actual benefit is compared to lower values.
What R-value measures
R-value is a measure of thermal resistance — how well a material resists heat flow. Higher R-values mean better insulation. R-60 means the insulation assembly has a thermal resistance of 60 (measured in h·ft²·°F/BTU in imperial units). For comparison, most Ontario homes built before 1990 have attic insulation in the R-12 to R-24 range.
Why R-60 specifically?
R-60 became the standard Ontario attic target because it represents the point of diminishing returns in most climate zones. Going from R-12 to R-24 cuts heat loss through the attic roughly in half. Going from R-24 to R-40 cuts it by another third. Going from R-40 to R-60 provides further improvement but at a declining rate. R-60 is roughly where the cost of adding more insulation exceeds the value of the energy it saves over a reasonable lifespan.
Key point: The HRS Program rebate for attic insulation is based on the improvement in R-value, not the final R-value reached. A home going from R-12 to R-60 receives a larger rebate than one going from R-40 to R-60. The biggest rebate opportunity is in homes with the least existing insulation.
How much insulation does R-60 require?
The depth of insulation needed to achieve R-60 depends on the material:
- Cellulose blown-in (R-3.7/inch): approximately 16 inches total depth
- Fibreglass blown-in (R-2.5/inch): approximately 24 inches total depth
- Closed-cell spray foam (R-6/inch): approximately 10 inches — rarely used for attic floors due to cost
Most homes have some existing insulation — typically fibreglass batts between joists. A contractor measures current depth and R-value, then calculates how much additional blown-in material is needed to reach the target.
Is R-60 always the right target?
For most Ontario homes, R-60 is a reasonable target if you're doing the work anyway and rebates are available. But if your home has R-40 already, the incremental benefit from topping up to R-60 is modest — and if budget is limited, spending the same money on air sealing may deliver more meaningful energy reduction than adding the last 20 points of R-value.
This is exactly the kind of decision an energy audit clarifies: your specific home's blower door result tells you whether air sealing or more insulation is the better next dollar spent.
Rebate implications
The HRS Program and Enbridge rebates both tie attic insulation rebates to achieved R-value improvement. The post-retrofit EnerGuide audit measures the actual installed depth and calculates the resulting R-value. For homeowners starting with very low insulation levels (R-12 or lower), achieving R-60 typically qualifies for the maximum available rebate under both programs.