Insulation R-Value Calculator
R-Value by Insulation Type & Thickness
Calculate R-value from insulation type and installed thickness
Thickness for Target R-Value
Calculate how many inches of insulation needed for a target R-value
Formula
R-Value = R per Inch x Thickness | Thickness = Target R / R per Inch | Heat Loss = Area / R-value (BTU/hr per degree F)
Frequently Asked Questions
What R-value do I need for my attic?
The recommended attic R-value depends on your climate zone. Zone 1 (hot): R-30 to R-49. Zone 2-3: R-38 to R-49. Zone 4-5 (cold): R-49 to R-60. Most existing homes benefit from adding insulation to reach R-49 in the attic.
Is a higher R-value always better?
Higher R-values provide more thermal resistance, but there is a point of diminishing returns. Going from R-11 to R-19 saves significantly more energy than going from R-38 to R-49. The most cost-effective approach is to insulate to the code-recommended level for your climate zone.
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