Cellulose Insulation Calculator

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Cellulose Insulation Calculator

R-13 (Walls/Floors) R-19 (Crawl Spaces) R-30 (Warm Climate Attic) R-38 (Standard Attic) R-49 (Cold Climate Attic) R-60 (High Efficiency Attic)

Project Estimates

function calculateInsulation() { var area = parseFloat(document.getElementById('areaSqFt').value); var rValue = parseInt(document.getElementById('targetRValue').value); var bagPrice = parseFloat(document.getElementById('costPerBag').value); var waste = parseFloat(document.getElementById('wastageFactor').value) / 100; if (isNaN(area) || area <= 0) { alert("Please enter a valid area."); return; } // Standards for common loose-fill cellulose (approx 19lb – 25lb bags) // Coverage values (sq ft per bag) and thickness (inches) vary by manufacturer. // These averages are based on standard blown-in cellulose charts. var coveragePerBag = 0; var depthInches = 0; if (rValue === 13) { coveragePerBag = 72; depthInches = 3.8; } else if (rValue === 19) { coveragePerBag = 49; depthInches = 5.5; } else if (rValue === 30) { coveragePerBag = 31; depthInches = 8.7; } else if (rValue === 38) { coveragePerBag = 24; depthInches = 11.0; } else if (rValue === 49) { coveragePerBag = 18; depthInches = 14.2; } else if (rValue === 60) { coveragePerBag = 14; depthInches = 17.4; } var bagsNeeded = Math.ceil((area / coveragePerBag) * (1 + waste)); var totalCost = bagsNeeded * bagPrice; var totalWeight = bagsNeeded * 25; // Average 25lb bag document.getElementById('bagsNeededResult').innerHTML = "Total Bags Required: " + bagsNeeded + ""; document.getElementById('thicknessResult').innerHTML = "Recommended Settled Thickness: " + depthInches + " inches"; document.getElementById('totalCostResult').innerHTML = "Estimated Material Cost: $" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('weightResult').innerText = "Estimated total material weight: ~" + totalWeight + " lbs (Assumes 25lb bags)"; document.getElementById('celluloseResult').style.display = "block"; }

How to Calculate Cellulose Insulation Needs

Upgrading your attic insulation with blown-in cellulose is one of the most cost-effective ways to improve home energy efficiency. Cellulose is primarily made from recycled newspaper treated with fire retardants, making it an eco-friendly alternative to fiberglass.

Understanding R-Value and Coverage

The R-Value measures the material's resistance to heat flow. The higher the R-value, the better the insulating power. For attics, the Department of Energy typically recommends R-38 for temperate climates and up to R-60 for very cold northern climates.

Unlike fiberglass batts, cellulose coverage is not linear. As you blow more insulation into a space, the material at the bottom compresses. To achieve a high R-value like R-49, you need significantly more bags per square foot than for R-19 because you must account for this "settled density."

The Calculation Formula

Our calculator uses industry-standard coverage charts for loose-fill cellulose. The basic math follows this logic:

  1. Determine Area: Measure the length and width of your attic or wall cavity (e.g., 25 ft x 40 ft = 1,000 sq ft).
  2. Identify Target R-Value: Choose based on your local building codes or climate zone.
  3. Lookup Bag Coverage: A standard bag covers less area as the R-value increases. For R-38, one bag typically covers 24 sq ft.
  4. Add Wastage: We recommend adding 5-10% to account for spillage and uneven distribution.

Example Calculation

Project: 1,200 sq ft attic in a cold climate (Targeting R-49)

Coverage: At R-49, one bag covers approx. 18 sq ft.

Math: 1,200 / 18 = 66.6 bags.

With 5% Waste: 66.6 * 1.05 = ~70 bags.

Estimated Cost: At $15/bag, the total would be $1,050.

Key Installation Tips

  • Baffles are Critical: Install rafter vents (baffles) at the eaves to ensure your soffit vents aren't blocked, which prevents attic mold.
  • Air Sealing First: Blown-in insulation stops heat transfer but not air leaks. Use spray foam or caulk to seal wire penetrations and plumbing stacks before blowing the cellulose.
  • Machine Rental: Most home improvement stores offer free blower rentals if you purchase a minimum number of bags (usually 20+).
  • Safety Gear: Cellulose is dusty. Always wear a N95 mask, eye protection, and long sleeves during installation.

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