Use this as a planning worksheet before comparing attic insulation bids. It does not replace contractor measurements, a blower-door test, moisture inspection, ventilation review, code guidance, or an energy audit.
Project Inputs
Use quoted all-in insulation price, or load a type preset.
Leave at 0 to estimate from the R-value gap.
Attic hatch, duct sealing, pest cleanup, mold or access allowance.
Leave at $0 to finance only the cash shortfall.
Optional comfort check for payment minus energy savings.
Estimated Attic Insulation Plan
Review bids
Cost Breakdown
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Recommendation Details
Methodology
The calculator estimates added R-value as target R-value minus current R-value, floored at zero. If added depth is left at zero, depth is estimated from the insulation type's approximate R-value per inch: 2.7 for blown fiberglass, 3.5 for blown cellulose, and 5.5 for spray foam or custom projects.
Insulation cost equals attic square footage multiplied by the entered installed cost per square foot. Add-ons include air sealing, old insulation removal, ventilation or baffle work, other attic allowances, and contingency applied to the subtotal before rebates.
Net project cost equals gross project cost minus entered rebates or tax credits, floored at zero. Cash shortfall or surplus compares cash available with net project cost. If no financing amount is entered, the calculator assumes the cash shortfall is financed; otherwise it uses the entered financing amount.
Monthly financing payment uses a standard amortizing payment formula. Simple payback divides net project cost by entered monthly energy savings. Effective monthly cost equals financing payment minus expected monthly energy savings.
Important caveats
- Contractor quotes should specify attic area, existing insulation depth and condition, target R-value, material type, installed depth, dense spots, air sealing scope, and cleanup.
- Air sealing usually belongs before new insulation. Sealing attic hatches, top plates, plumbing and electrical penetrations, chases, ducts, and recessed lights can materially change savings and comfort.
- Ventilation, soffit baffles, bath fan venting, vapor control, roof leaks, ice dam risk, and moisture conditions should be corrected before burying problems under new insulation.
- Local climate, utility rates, HVAC efficiency, duct location, thermostat behavior, and actual energy-audit results can make savings higher or lower than the entered estimate.
- Rebates and tax credits may depend on program rules, documentation, qualified products, tax liability, contractor licensing, and timing. Confirm eligibility before relying on incentives.
- Pest contamination, mold, asbestos, knob-and-tube wiring, recessed light clearance, fire blocking, unsafe attic access, or wet old insulation can require extra remediation.
- This calculator is for planning. It is not financial, tax, engineering, code, energy-audit, building-science, or contractor advice.