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Insulation Calculator

Free insulation calculator. Calculate batts, rolls, or blown-in insulation needed by R-value, area, and insulation type for any project.

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sq ft

Insulation Estimate

Coverage Area1,000 sq ft
LocationAttic
Insulation TypeFiberglass Batts
Target R-ValueR-30
R-Value per Inch3.2
Thickness Needed9.4 inches
Batts Needed12 batts

Estimated Total Cost

$1,500.00

Total Cost$1,500.00
Materials50%
Labor50%

12,800+ estimates calculated this month

Recommended R-Values by Location:
  • Walls: R-13 to R-21
  • Attic: R-30 to R-60
  • Floor / Crawlspace: R-19 to R-30

Insulation R-Value & Cost Guide

Required R-values by climate zone, material comparisons, and energy savings data.

What R-Value Insulation Do I Need?

Required R-values vary by climate zone, ranging from R-13 walls/R-30 attic (South) to R-21 walls/R-60 attic (North).

  • Zone 1-2 (Southern US): R-13 walls, R-30 attic, R-13 floors
  • Zone 3-4 (Mid-Atlantic, Midwest): R-15–R-20 walls, R-38–R-49 attic
  • Zone 5-6 (Northern US): R-20–R-21 walls, R-49–R-60 attic
  • Zone 7-8 (Alaska, extreme cold): R-21+ walls, R-60+ attic

R-value is additive. A 2×4 wall with R-13 batts + R-5 continuous foam sheathing = R-18 total.

Key Takeaways

  • Southern US: R-13 walls, R-30 attic
  • Northern US: R-20+ walls, R-49–R-60 attic
  • R-values are additive when layered

Insulation Types & Cost Comparison

Fiberglass batts are the cheapest at $0.50–$1.50/sq ft installed, while closed-cell spray foam costs $1.50–$3.50/sq ft but provides the highest R-value per inch.

  • Fiberglass batts: $0.50–$1.50/sq ft, R-3.1–R-3.7 per inch
  • Blown-in fiberglass: $0.75–$1.50/sq ft, R-2.5–R-3.7 per inch
  • Cellulose (blown): $0.75–$1.25/sq ft, R-3.2–R-3.8 per inch
  • Open-cell spray foam: $0.75–$1.50/sq ft, R-3.5–R-3.7 per inch
  • Closed-cell spray foam: $1.50–$3.50/sq ft, R-6.0–R-7.0 per inch
  • Rigid foam board (XPS): $0.75–$2.00/sq ft, R-5.0 per inch

Key Takeaways

  • Fiberglass batts: cheapest at $0.50–$1.50/sq ft
  • Closed-cell spray foam: highest R per inch (R-6–R-7)
  • Cellulose: best value for attic blown-in

Where to Insulate for Maximum Energy Savings

Attic insulation provides the highest ROI — insulating an uninsulated attic can reduce heating/cooling bills by 25–40%.

  • Attic (highest priority): Blown cellulose or fiberglass to R-38–R-60
  • Exterior walls: Batts or blown-in to R-13–R-21 (new construction or gut remodel)
  • Crawl space/basement: R-10–R-19 on rim joists and walls
  • Ductwork: R-6–R-8 on exposed ducts in unconditioned spaces

Sealing air leaks before insulating is critical. Air sealing alone can reduce energy costs by 10–20%. Insulation without air sealing loses much of its effectiveness.

Key Takeaways

  • Attic insulation: highest ROI (25–40% savings)
  • Seal air leaks before insulating
  • Duct insulation: R-6–R-8 in unconditioned spaces

How to Use This Calculator

Enter the area to insulate

Input the total square footage of walls, attic, floor, or crawlspace you need to insulate.

Select location and R-value

Choose where the insulation will be installed and the desired R-value based on your climate zone and building code requirements.

Choose insulation type

Pick from fiberglass batts, blown-in fiberglass, blown-in cellulose, open-cell spray foam, or closed-cell spray foam.

Review thickness and cost breakdown

See the required thickness, number of batts or bags needed, plus a material and labor cost estimate.

Insulation Calculation Formulas

Thickness = R-Value / R-per-Inch
Units Needed = Area / Coverage per Unit
Material Cost = Area x Cost per Sq Ft
Labor Cost = Area x Labor Rate per Sq Ft
Total Cost = Material Cost + Labor Cost

Where:

R-per-Inch
= Fiberglass 3.2, Cellulose 3.5, Open-Cell 3.7, Closed-Cell 6.5
Coverage per Unit
= Varies by product: 88 sf/batt, 40 sf/bag, etc.

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Frequently Asked Questions

What R-value do I need for my attic?
Most building codes recommend R-38 to R-60 for attics in cold climates and R-30 to R-38 in moderate climates. The Department of Energy provides zone-specific recommendations, but R-38 is a good baseline for most U.S. homes.
How thick does insulation need to be?
Thickness depends on the insulation type and target R-value. For example, fiberglass batts provide about R-3.2 per inch, so R-30 requires roughly 9.4 inches. Closed-cell spray foam at R-6.5 per inch only needs about 4.6 inches for the same R-value.
Is blown-in insulation better than batts?
Blown-in insulation fills gaps and irregular spaces more completely, making it ideal for attics and retrofit projects. Batts work well in new construction with standard stud spacing. Both achieve similar R-values per inch; the best choice depends on your application.
How much does spray foam insulation cost?
Open-cell spray foam typically costs $1.00 to $1.50 per square foot installed, while closed-cell runs $1.50 to $3.50 per square foot. Closed-cell provides a higher R-value per inch and acts as a vapor barrier, which can offset the higher cost in moisture-prone areas.
Can I install insulation myself?
Fiberglass batts and blown-in cellulose are popular DIY-friendly options. Blown-in requires renting a blower machine. Spray foam insulation is best left to professionals due to the specialized equipment and safety requirements. Always wear proper protective gear when handling insulation.

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