Insulation Calculator
Calculate batts, rolls, or blown-in insulation needed for walls, attics, and crawl spaces.
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How to Calculate Insulation
Measure total area to insulate. For batts, divide area by coverage per roll/pack. For blown-in, calculate area and select depth based on your target R-value — bag counts are calculated using standard cellulose coverage rates (bag label values vary; check your specific product).
Frequently Asked Questions
What R-value do I need?
Depends on your climate. Mild climates: R-2.5 to R-4.0 (walls), R-4.0 to R-6.0 (ceilings). Cold climates: R-4.0 to R-6.0 (walls), R-6.0 to R-8.0 (ceilings). In US zones: R-13 to R-21 walls, R-30 to R-60 attics. Check your local energy code.
How many rolls of insulation do I need?
Measure total area between studs or joists. Rolls typically cover 3.7-8.2 m² (40-88 sq ft) depending on width and length. Check product packaging and buy 5-10% extra for cuts.
How much does insulation cost?
Fiberglass batts: $0.50-$1.50 per sq ft. Blown-in cellulose: $1-$2 per sq ft. Spray foam (closed cell): $1.50-$3.50 per sq ft. Professional installation adds 50-100% to material costs.
Should I use batts or blown-in insulation?
Batts are easier for open walls during new construction. Blown-in is better for existing walls (no tear-out needed) and irregular attic spaces. Blown-in fills gaps better around wiring and pipes. Both achieve similar R-values per inch.
Can I add insulation over existing insulation?
Yes, in attics you can add unfaced batts or blown-in on top of existing insulation. Do not use faced batts over existing insulation — the vapour barrier creates a moisture trap. Ensure no mould or water damage exists before adding more.