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Attic Insulation Calculator

Attic Area (sq ft)

Current R-Value

Target R-Value

Insulation Type

Climate Zone

Waste Factor

Result

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◆ LIVE 3D PREVIEW

Added Depth

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Cost

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How to Calculate Attic Insulation

Use this free attic insulation calculator to get instant, accurate results for your construction project. Simply enter your measurements above and the calculator will automatically compute the result using industry-standard formulas.

Pro Tip: Always add 10-15% extra material to account for waste, cuts, and job-site conditions. This is standard practice recommended by experienced contractors.

Related Calculators

▸ Attic Fan ▸ Attic Floor ▸ Batt Insulation ▸ Blown In Insulation ▸ Garage Insulation ▸ Home Insulation Cost

💡 Pro Tips — Attic Insulation

R-value targets: Attic R-49 to R-60, walls R-13 to R-21, floor R-25 to R-30.
Don't compress batts — squished insulation loses R-value. It needs full loft to work.
Vapor barrier goes on warm side — interior side in cold climates, exterior in hot.
Spray foam also air-seals — worth the premium in drafty old homes.
Blown-in is best for attics — fills all gaps and irregularities that batts miss.

📊 R-Value by Climate Zone

Zone	Attic	Walls	Floor
1-2	R-30 to R-49	R-13	R-13
3-4	R-38 to R-60	R-13 to R-21	R-19
5-6	R-49 to R-60	R-20+	R-25 to R-30

❓ Frequently Asked Questions

+What R-value do I need?

Depends on climate zone. Attics: R-30 to R-60. Walls: R-13 to R-21. Floors: R-13 to R-30. Check your local energy code.

+Which insulation type is best?

Batts: cheapest, DIY-friendly. Blown-in: best for attics. Spray foam: best air sealing + highest R per inch. Each has its place.

+Does old insulation need removal?

Usually no — you can add new insulation on top. Exception: if it is wet, moldy, or contains vermiculite (potential asbestos source).

+Where does air really leak?

Top air leak spots: attic hatches, recessed lights, plumbing/duct penetrations, electrical outlets on exterior walls, and rim joists.