Attic Insulation Calculator
Calculate the required insulation R-value, material volume, and cost for your attic based on location, attic type, and dimensions.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Attic Insulation Calculator
- Select your climate zone – Choose from Hot (Zone 1) to Very Cold (Zone 4). This sets the recommended R-value.
- Choose attic type – Select Unheated (most common) or Heated (conditioned space). Heated attics require 30% less insulation.
- Enter attic dimensions – Provide Length and Width in feet (ft). Use decimal values if needed (e.g., 40.5).
- Enter current R-value – If you already have insulation, enter its R-value. Enter 0 if none exists.
- Pick insulation material – Choose from Fiberglass Batts (R-3.7/in), Cellulose (R-3.2/in), or Spray Foam (R-6.0/in).
- Set cost per square foot – Enter the material cost per sq ft (e.g., $0.50). This is used for the cost estimate.
- Click "Calculate Insulation" – The results show recommended R-value, needed R-value, inches of insulation, material volume (cubic ft), and estimated cost.
Tips:
- All measurements are in imperial units (feet, inches).
- Ensure all inputs are positive numbers. The form validates entries automatically.
- The breakdown explains each step of the calculation for transparency.
Previous Results
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Frequently Asked Questions
The recommended R-value depends on your climate zone. Zone 1 (hot) requires R-30, Zone 2 (mixed) R-38, Zone 3 (cold) R-49, and Zone 4 (very cold) R-60. For heated attics, reduce by 30%.
Measure the length and width of your attic floor in feet. Multiply them to get the square footage. If your attic has irregular shapes, divide into rectangles and sum the areas.
Fiberglass batts are cost-effective (R-3.7/in), cellulose is eco-friendly (R-3.2/in), and spray foam offers the highest R-value per inch (R-6.0/in) but is more expensive. Choose based on budget and needs.