Calculate how much insulation you need for walls, attics, or floors. Find the recommended R-value for your climate zone, get bag or roll counts, and see your total cost estimate.
Insulation type Batts · Blown-in · Rigid foam
sq ft
Total floor, wall, or attic area
R
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R-15 kraft batt roll: $35–$60
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Cellulose bag (~40 lbs): $18–$28
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2 in XPS 4×8 sheet: $30–$50
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bags needed
Blown-in cellulose
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Square feet
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Target R-value
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Material cost
R-0Target: R-49R-60
Area to insulate—
Insulation type / material—
R-value per inch—
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DOE recommended R-values by zone
Zone 1–2 (Hot South)
Attic: R-30 to R-49 Wall: R-13 Floor: R-13
Zone 3 (Mixed South)
Attic: R-38 to R-60 Wall: R-13 to R-15 Floor: R-19 to R-25
Zone 4 (Mixed Mid)
Attic: R-38 to R-60 Wall: R-13 to R-21 Floor: R-25 to R-30
Zone 5–6 (Cool/Cold)
Attic: R-49 to R-60 Wall: R-13 to R-21 Floor: R-25 to R-30
Zone 7–8 (Very Cold)
Attic: R-49 to R-60 Wall: R-21 to R-30 Floor: R-25 to R-38
Frequently asked questions
What R-value do I need for my attic? ›
The Department of Energy recommends R-49 to R-60 for attics in most US climate zones (5–7), R-38 for zones 3–4, and R-30 minimum for the hot South (zones 1–2). Most existing homes have R-11 to R-19 in the attic — significantly below current recommendations. Adding insulation to an under-insulated attic is typically the single highest-return energy efficiency improvement for most homes.
What is the difference between blown-in and batt insulation? ›
Batt (or roll) insulation comes in pre-cut sections sized for standard stud and joist spacing. It's easy to DIY and works best in open wall cavities and between joists. Blown-in insulation (cellulose or fiberglass) is blown with a machine into attic floors or closed cavities. It conforms to irregular shapes and covers better, but requires a blowing machine (usually free with bag purchase at home improvement stores) or a professional installer.
Can I add new insulation on top of old insulation? ›
Yes, for attics you can usually add new blown-in or unfaced batts directly on top of existing insulation to reach your target R-value. Run the new layer perpendicular to existing batts to cover gaps. Do not add faced (kraft paper or foil) batts on top — the vapor barrier should always face the warm side of the assembly, and adding a second vapor barrier in the middle of the assembly can trap moisture. For walls, adding insulation is more complex and usually requires a contractor.
How much does attic insulation cost? ›
DIY blown-in cellulose costs $0.25–$0.50 per square foot in materials. A 1,200 sq ft attic insulated to R-38 with cellulose costs roughly $300–$600 in materials. Professionally installed blown-in insulation runs $1.50–$3.00 per sq ft installed ($1,800–$3,600 for the same attic). Batt insulation for a 1,200 sq ft attic costs $600–$1,200 in materials installed DIY. Many utilities offer rebates for energy efficiency improvements — check your local utility's website.
About this insulation calculator
This calculator supports three insulation types — batt/roll, blown-in, and rigid foam board — each with material-specific R-value per inch. It uses the DOE climate zone recommendations to suggest a target R-value for your location and application, then calculates the quantity and cost. The R-value progress bar shows how close your planned insulation is to the recommended target.
Rebates and incentives
The Inflation Reduction Act (2022) provides a federal tax credit of up to 30% of insulation material costs (up to $1,200/year) for qualifying energy efficiency improvements. Many state and local utilities offer additional rebates. Check DSIRE.org for incentives available in your area before purchasing.