Insulation Calculator

Insulation's R-value measures its resistance to heat flow — the higher the number, the better it keeps your home warm in winter and cool in summer. Select your space type, enter your length and width, then choose your framing depth, framing spacing, insulation type, and target R-value to get the required insulation thickness. Secondary outputs include total area, material needed (in bags), your current R-value, and the additional R-value needed if you already have existing insulation in place.

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Results

Required Insulation Thickness

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Total Area

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Material Needed

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Current R-Value

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Additional R-Value Needed

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Frequently Asked Questions

What is R-value and why is it important?

R-value measures thermal resistance - how well insulation resists heat flow. Higher R-values mean better insulating performance. The right R-value depends on your climate zone and the area being insulated (attic, walls, basement).

How thick should insulation be in an attic?

Attic insulation thickness varies by R-value target and material type. For R-30, you typically need 8-10 inches of blown-in fiberglass, 10-14 inches of cellulose, or 6-8 inches of fiberglass batts.

Can I add new insulation over existing insulation?

Yes, you can usually add new insulation over existing insulation to increase the total R-value. Make sure the existing insulation is dry and in good condition. The new insulation should be unfaced to prevent vapor barrier issues.

What's the difference between batt and blown-in insulation?

Batt insulation comes in pre-cut panels that fit between studs, while blown-in insulation is loose material installed with special equipment. Blown-in provides better coverage around obstacles and irregular spaces.

How many square feet does a bag of insulation cover?

Coverage varies by insulation type and target R-value. A typical bag of blown-in fiberglass covers 40-60 square feet at R-30, while cellulose covers 25-40 square feet. Check manufacturer specifications for exact coverage.

Do I need different R-values for walls versus attics?

Yes, different areas require different R-values. Attics typically need R-30 to R-60, exterior walls need R-13 to R-21, and basements need R-10 to R-15, depending on your climate zone.

Should I hire a professional or install insulation myself?

Batt insulation in accessible areas can be DIY-friendly. However, blown-in insulation requires special equipment and expertise. Consider professional installation for spray foam, dense-pack applications, or hard-to-reach areas.

How much can proper insulation save on energy bills?

Proper insulation can reduce heating and cooling costs by 15-50% depending on your current insulation levels and climate. The investment typically pays for itself within 2-10 years through energy savings.