What R-Value of Insulation Do I Need?

What R-value means

R-value measures resistance to heat flow — higher is better. Walls and attics need different amounts, and the right target depends on your climate zone, so check your local energy code for specifics.

• Walls: roughly R-13 (2×4 studs) to R-21 (2×6 studs).
• Attics: often R-38 to R-49 in colder climates.
• Floors over unheated space: around R-19 to R-30.

Try it Insulation Calculator → Find how many bags or bundles of insulation you need for an area at a given R-value, with a rough cost.

Higher R-value = fewer square feet per bag

A higher R-value means a thicker product, so each bag or bundle covers less floor area. That's why our calculator asks for the R-value: coverage per bag drops from about 106 sq ft at R-13 to roughly 42 sq ft at R-49.

Install it right

Air-seal gaps and penetrations first — insulation slows heat, it doesn't stop drafts. Don't compress batts to fit; squashed insulation loses much of its R-value. Wear a respirator, gloves and long sleeves.