Insulation R-Value & Batts Calculator
Calculate insulation R-value needed and number of batts required for an area.
What this calculates
Insulation R-value measures resistance to heat flow — higher is better. US DOE recommends R-49 to R-60 for attics in cold climates, R-30 to R-49 in warm. This calculator estimates the number of batts needed for any area at a given R-value (assumes standard 16" or 24" on-center framing).
Formula & how it works
Batts needed = ceil(area / coverage_per_batt). Standard batt sizes: R-13 (3.5" thick) = 40 sf/batt, R-19 (6.25") = 32, R-30 (9.5") = 24, R-38 (12") = 21, R-49 (15.5") = 16.
Worked example
1,200 sq ft attic, R-49 batts. Batts = ceil(1200 / 16) = 75 batts.
Frequently asked questions
Climate zones?
DOE zone 1-2 (warm): attic R-30-49. Zone 3-4: R-38-49. Zone 5-7 (cold): R-49-60.
Loose-fill vs batts?
Loose-fill blown insulation gets better coverage around obstacles. Same R/inch, cheaper for large attics.
Stacking batts?
Yes — perpendicular layers eliminate thermal bridging through framing.
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