Insulation Optimal Thickness Calculator

Determine the insulation thickness needed to reach a target R-value and estimate project cost based on material conductivity, area, and existing insulation.

Desired total thermal resistance.
Use manufacturer lambda value.
Surface area being insulated.
Optional. Defaults to 0 if blank.
Optional. Defaults to $0.00 if blank.
Optional. Defaults to $0.00 if blank.

Budgetary planning aid; verify code compliance and installation details with a qualified contractor.

Examples

  • Target R 5, conductivity 0.037, area 40 m², existing R 1.2, $140/m³ material, $18/m² labor ⇒ Thickness 0.14 m | U-value 0.20 W/m²·K | Cost $1,507.36
  • Target R 3.5, conductivity 0.045, area 22 m², blank optional costs ⇒ Thickness 0.16 m | U-value 0.29 W/m²·K | Cost $0.00

FAQ

How do I find the material conductivity?

Manufacturers publish lambda values (W/m·K) on product data sheets; enter that number directly.

What if my existing insulation already meets the target?

If existing R-value exceeds the target, the calculator returns zero thickness and cost, indicating no additional layer is required.

Can I mix materials in the same assembly?

Yes. Sum the R-values of each layer and enter the total as the existing R-value before calculating the new layer.

Does the cost include vapour barriers or fasteners?

No. Add extras like membranes, tapes, or fasteners manually to the final budget if they are needed for your build-up.

Additional Information

  • Thickness equals required additional R-value multiplied by the insulation's thermal conductivity.
  • U-value is the inverse of total R-value, showing overall heat transfer after the upgrade.
  • Material volume is area × thickness, allowing quick budget estimates when unit pricing is per cubic metre.

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