Dense Pack Cellulose Calculator

Dense pack cellulose is a highly effective insulation method that creates a super-insulated and airtight building envelope. It involves blowing specially treated, recycled paper fibers into enclosed cavities like walls, floors, and ceilings at a high density. This calculator helps you estimate the amount of cellulose material you'll need for your project, ensuring you purchase the right quantity for optimal performance.

Project Dimensions & Settings

function calculateCellulose() { var length = parseFloat(document.getElementById('totalLength').value); var height = parseFloat(document.getElementById('wallHeight').value); var depthInches = parseFloat(document.getElementById('cavityDepth').value); var spacing = parseFloat(document.getElementById('studSpacing').value); var density = parseFloat(document.getElementById('desiredDensity').value); var bagWeight = parseFloat(document.getElementById('bagWeight').value); var costPerBag = parseFloat(document.getElementById('costPerBag').value); var resultDiv = document.getElementById('result'); if (isNaN(length) || isNaN(height) || isNaN(depthInches) || isNaN(spacing) || isNaN(density) || isNaN(bagWeight)) { resultDiv.innerHTML = 'Please enter valid numbers in all required fields.'; return; } if (length <= 0 || height <= 0 || depthInches <= 0 || spacing <= 0 || density <= 0 || bagWeight <= 0) { resultDiv.innerHTML = 'All input values must be greater than zero.'; return; } // Standard stud thickness is 1.5 inches var studThicknessInches = 1.5; // Convert dimensions to feet var depthFeet = depthInches / 12; var studThicknessFeet = studThicknessInches / 12; // Calculate gross volume of the cavity var grossVolume = length * height * depthFeet; // Calculate the volume of the studs to subtract var numberOfStuds = Math.floor((length * 12) / spacing) + 1; var singleStudVolume = studThicknessFeet * depthFeet * height; var totalStudVolume = numberOfStuds * singleStudVolume; // Calculate the net volume to be filled with insulation var netVolume = grossVolume – totalStudVolume; if (netVolume < 0) { netVolume = 0; // Avoid negative results if inputs are illogical } // Calculate total weight of cellulose needed var totalWeightNeeded = netVolume * density; // Calculate number of bags, rounding up to the nearest whole bag var numberOfBags = Math.ceil(totalWeightNeeded / bagWeight); var output = '

Calculation Results:

'; output += '

'; output += '
• Net Insulation Volume: ' + netVolume.toFixed(2) + ' cubic feet
'; output += '
• Total Cellulose Weight Required: ' + totalWeightNeeded.toFixed(2) + ' lbs
'; output += '
• Number of Bags Needed: ' + numberOfBags + '
'; if (!isNaN(costPerBag) && costPerBag > 0) { var totalCost = numberOfBags * costPerBag; output += '
• Estimated Material Cost: $' + totalCost.toFixed(2) + '
'; } output += '

'; resultDiv.innerHTML = output; }

Understanding the Calculation

This calculator determines your material needs by following a simple, logical process:

1. Calculate Gross Volume: It first calculates the total volume of the wall cavities (Length x Height x Depth) as if they were empty.
2. Subtract Framing Volume: It then estimates the volume occupied by wood framing (studs) based on your specified spacing and subtracts this from the gross volume. This gives the 'Net Volume' that actually needs to be filled with insulation.
3. Determine Total Weight: The net volume is multiplied by the target density (typically 3.5 lbs/ft³ for walls) to find the total weight of cellulose required.
4. Calculate Bags Needed: Finally, it divides the total weight by the weight of a single bag and rounds up to the nearest whole number, since you can't purchase a fraction of a bag.

Example Calculation

Let's say you have a 40-foot long exterior wall that is 8 feet high. The wall is built with 2×6 studs, so the cavity depth is 5.5 inches. Studs are 16 inches on center.

• Gross Volume: 40 ft x 8 ft x (5.5 / 12 ft) = 146.67 cubic feet
• Stud Volume: The calculator estimates the volume of the studs and subtracts it, resulting in a Net Volume of approximately 132.5 cubic feet.
• Total Weight: 132.5 ft³ x 3.5 lbs/ft³ = 463.75 lbs of cellulose.
• Bags Needed: 463.75 lbs / 25 lbs/bag = 18.55 bags. This is rounded up to 19 bags.

What is Dense Pack Cellulose?

Cellulose insulation is primarily made from recycled newsprint and other paper sources, which are then treated with non-toxic borate compounds. This treatment gives the material its Class-A fire rating and makes it resistant to mold, pests, and rot. During installation, a specialized machine blows the fluffy material through hoses into the building cavities at a high pressure, ensuring a tight fit that leaves no gaps or voids.

Key Benefits of Dense Packing

• Superior Air Sealing: Unlike batts, dense pack cellulose flows around pipes, wires, and outlets, completely filling the cavity and drastically reducing air infiltration. This is one of its biggest advantages over other insulation types.
• Prevents Settling: When installed at the correct density (around 3.5 lbs/ft³ in walls), the material is self-supporting and will not settle over time, maintaining its R-value for the life of the building.
• Excellent Soundproofing: The density and fibrous nature of cellulose make it an exceptional sound-dampening material, helping to create a quieter indoor environment.
• Moisture Management: Cellulose can safely absorb and release moisture without compromising its structural integrity or R-value, helping to manage humidity within the wall assembly.
• Environmentally Friendly: With a high recycled content (often over 85%), it is one of the greenest insulation products available.