Blow-In Insulation Calculator

Estimate the amount of insulation needed and its cost for your project.

Insulation Project Details

This calculator helps you determine the required R-value for your climate and space, then calculates the volume of blow-in insulation needed. It also estimates material costs based on typical product prices and coverage.

Insulation Project Data

Insulation Coverage Chart (Approximate)

Insulation Type	Typical Density (lbs/cu ft)	Coverage per Bag (sq ft @ 1-inch)	Typical Bag Cost ($)	Example R-Value per Inch
Fiberglass (Loose Fill)	0.5 – 1.5	150 – 250	$40 – $60	~3.0 – 4.0
Cellulose (Loose Fill)	1.5 – 3.0	100 – 200	$35 – $55	~3.5 – 4.5
Mineral Wool (Loose Fill)	1.0 – 2.0	120 – 180	$50 – $70	~3.5 – 4.5

Insulation Depth vs. R-Value

What is Blow-In Insulation?

Blow-in insulation, also known as loose-fill insulation, is a type of insulation material that is installed by blowing it into place using specialized equipment. It’s commonly used for insulating attics, walls, and floors. The primary materials used for blow-in insulation are fiberglass and cellulose, though mineral wool and other materials are also available. This method is particularly effective for filling irregular spaces, sealing air gaps, and achieving a high R-value without seams or voids that can compromise thermal performance. It’s a popular choice for both new construction and retrofitting existing homes to improve energy efficiency and comfort.

Who should use it: Homeowners and contractors looking to improve the thermal performance of attics, walls (especially in existing homes where access is limited), floors, and crawl spaces. It’s ideal for areas with complex framing, numerous obstructions, or where achieving a continuous layer of insulation is challenging with batts or rolls. It is also a preferred method for achieving higher R-values in thicker applications, common in colder climates.

Common misconceptions: A common misconception is that all blow-in insulation is the same. In reality, the type of material (fiberglass vs. cellulose), its density, and the R-value it provides per inch can vary significantly. Another myth is that it’s only for attics; it’s highly effective in wall cavities too, especially during renovations. Some believe it’s a messy or difficult process, but with professional installation, it’s efficient and creates a seamless thermal barrier.

Blow-In Insulation Calculation Formula and Mathematical Explanation

Calculating the required amount of blow-in insulation involves several steps, ensuring you achieve the target thermal resistance (R-value) for your space. The core idea is to determine the total volume of insulation needed based on the area, desired thickness, and then convert that volume into the number of bags required, considering the product’s coverage and density.

Step 1: Determine the R-Value Difference Needed

If you have existing insulation, you first need to find out how much more R-value you need to add to reach your target.

R-Value Difference = Desired R-Value - Current Insulation R-Value

Step 2: Calculate Required Insulation Thickness

Knowing the R-value per inch for your chosen insulation material (a property usually listed by the manufacturer), you can calculate the required thickness.

Required Thickness (inches) = R-Value Difference / (R-Value per Inch)

Note: If you are starting with no insulation (Current R-Value = 0), then the Desired R-Value is what you need to achieve, and this formula still applies. The calculator simplifies this by calculating the thickness needed to reach the *total* desired R-value if no current insulation is present, or the additional thickness needed if there is. For simplicity and broader application, our calculator directly calculates the thickness needed to achieve the target R-value directly, assuming the input ‘Desired R-Value’ is the final goal, and ‘Current Insulation R-Value’ is accounted for indirectly by the fact that you’re adding to it. A more precise calculation would account for the R-value of the existing layer when calculating the final thickness needed, but for practical purposes, estimating based on target R-value and coverage is common. The calculator below focuses on the required thickness to achieve the *total* R-value desired, implicitly assuming the existing insulation’s R-value is less than the target. A more direct calculation uses the R-value per inch for the *new* insulation being added. The formula used here directly calculates the thickness needed to achieve the total desired R-value based on the properties of the *new* insulation being installed. This is often a simplification but practical. The true calculation is thickness = R_needed / R_per_inch. If starting fresh, R_needed = Desired R-value. If adding, R_needed = Desired R-value – R_current. The calculator uses the practical approach where “Desired R-Value” is the target and “Required Thickness” is calculated from that target assuming the new insulation provides that R-value contribution.

A simplified and common approach for blow-in calculators is to determine the thickness required to achieve the *total* desired R-value, based on the R-value per inch of the *new* insulation being installed. The calculator uses this practical method: it determines the thickness needed to reach the Desired R-Value directly.

Required Thickness (inches) = Desired R-Value / R-Value per Inch of New Insulation

Step 3: Calculate Total Insulation Volume Needed

Convert the required thickness into a volume by multiplying by the area.

Total Volume (cubic feet) = (Area (sq ft) * Required Thickness (inches)) / 12

Step 4: Calculate Total Cubic Feet per Bag

The coverage is usually given per inch. We need to find out how many cubic feet are in one bag.

Cubic Feet per Bag = (Coverage per Bag (sq ft @ 1-inch) * 1 inch) / 12

Step 5: Calculate Total Bags Needed

Divide the total volume needed by the volume per bag. We round up to the nearest whole bag.

Total Bags Needed = Total Volume (cubic feet) / Cubic Feet per Bag

Step 6: Calculate Estimated Material Cost

Multiply the total number of bags by the cost per bag.

Estimated Material Cost = Total Bags Needed * Cost per Bag

Formula Variables

Variable	Meaning	Unit	Typical Range
Area	The total surface area to be insulated.	Square Feet (sq ft)	100 – 5000+
Desired R-Value	The target thermal resistance for the space.	R-value (unitless)	30 – 60 (attics, climate dependent)
Current Insulation R-Value	The R-value of insulation already present.	R-value (unitless)	0 – 40
R-Value per Inch (Implied)	Thermal resistance provided by the insulation material for each inch of thickness. This is derived from the product specifications. For calculation purposes in the calculator, we infer this from the user inputs related to coverage and desired R-value. The calculator directly calculates thickness needed to achieve the total R-value. A typical value for cellulose/fiberglass is 3.5-4.5 R/inch.	R-value/inch	3.0 – 4.5
Required Thickness	The calculated depth of insulation needed to achieve the desired R-value.	Inches	5 – 20+
Insulation Density	Weight of the insulation material per unit volume. Affects settling and performance.	lbs / cubic foot	0.5 – 3.0
Coverage per Bag	The area a bag of insulation can cover at a 1-inch depth.	sq ft @ 1-inch	100 – 250
Cost per Bag	The price of a single bag of insulation material.	$	$35 – $70
Total Bags Needed	The calculated number of bags required for the project.	Bags	Varies significantly
Estimated Material Cost	The total projected cost of the insulation material.	$	Varies significantly

Practical Examples (Real-World Use Cases)

Example 1: Attic Insulation Upgrade

A homeowner in a moderate climate wants to upgrade their attic insulation. The attic measures 1200 sq ft. Currently, there is about 6 inches of old insulation with an estimated R-value of R-19. The recommended R-value for their area is R-49. They find blow-in cellulose insulation costing $40 per bag, and each bag covers 180 sq ft at a 1-inch depth.

• Inputs:
  • Area: 1200 sq ft
  • Desired R-Value: 49
  • Current Insulation R-Value: 19
  • Cost per Bag: $40
  • Coverage per Bag (sq ft @ 1-inch): 180
  • Insulation Density: 2.0 lbs/cu ft (Typical for cellulose)
• Calculations:
  • R-Value Difference Needed: 49 – 19 = 30 R-value
  • Assuming the new cellulose provides R-4 per inch, Required Thickness = 30 R / 4 R/inch = 7.5 inches.
  • Total Volume = (1200 sq ft * 7.5 inches) / 12 = 750 cubic feet.
  • Cubic Feet per Bag = (180 sq ft * 1 inch) / 12 = 15 cubic feet.
  • Total Bags Needed = 750 cu ft / 15 cu ft/bag = 50 bags.
  • Estimated Material Cost = 50 bags * $40/bag = $2000.
• Interpretation: The homeowner needs approximately 50 bags of this specific cellulose insulation to achieve the target R-49, costing around $2000 for materials. This upgrade is expected to significantly reduce heating and cooling costs.

Example 2: New Wall Insulation

A contractor is building a new home in a cold climate and wants to insulate the exterior walls. The total wall area to be insulated is 1500 sq ft. The target R-value is R-21. They choose blow-in fiberglass insulation that costs $55 per bag and covers 220 sq ft at a 1-inch depth. The density is 1.2 lbs/cu ft.

• Inputs:
  • Area: 1500 sq ft
  • Desired R-Value: 21
  • Current Insulation R-Value: 0 (New construction)
  • Cost per Bag: $55
  • Coverage per Bag (sq ft @ 1-inch): 220
  • Insulation Density: 1.2 lbs/cu ft
• Calculations:
  • R-Value Difference Needed: 21 – 0 = 21 R-value
  • Assuming the new fiberglass provides R-3.8 per inch, Required Thickness = 21 R / 3.8 R/inch ≈ 5.53 inches.
  • Total Volume = (1500 sq ft * 5.53 inches) / 12 ≈ 691.25 cubic feet.
  • Cubic Feet per Bag = (220 sq ft * 1 inch) / 12 ≈ 18.33 cubic feet.
  • Total Bags Needed = 691.25 cu ft / 18.33 cu ft/bag ≈ 37.7 bags. Rounded up to 38 bags.
  • Estimated Material Cost = 38 bags * $55/bag = $2090.
• Interpretation: For the new home’s walls, approximately 38 bags of fiberglass insulation are needed, amounting to about $2090 in material costs, to achieve the R-21 target.

How to Use This Blow-In Insulation Calculator

Using our Blow-In Insulation Calculator is straightforward. Follow these steps to get an accurate estimate for your project:

1. Enter Area: Input the total square footage of the space you intend to insulate (e.g., attic floor area, wall surface area).
2. Specify Desired R-Value: Determine the recommended R-value for your climate zone and building type. Higher R-values provide better insulation. You can usually find this information from local building codes or energy efficiency resources.
3. Enter Current Insulation R-Value (Optional): If you are adding insulation to an existing layer, enter the estimated R-value of that current insulation. If it’s a new build or you’re removing old insulation, leave this blank or enter 0.
4. Input Insulation Product Details:
   • Insulation Density: Enter the density (lbs/cu ft) of the specific blow-in insulation product you plan to use. This information is typically found on the product packaging or manufacturer’s website.
   • Cost per Bag: Enter the price you expect to pay for one bag of the insulation material.
   • Coverage per Bag: This is a critical input. It tells you how many square feet one bag of insulation will cover when installed at a depth of 1 inch. This value is essential for calculating the required thickness and number of bags.
5. Calculate: Click the “Calculate” button. The calculator will process your inputs and display the results.

How to read results:

• Main Result (Total Bags Needed): This is the primary output, indicating the estimated number of bags required. Always round up to ensure you have enough material.
• Intermediate Values: You’ll see the calculated R-Value Difference, Required Thickness in inches, and Estimated Material Cost. These provide a breakdown of the calculation and the financial implication.
• Assumptions: The calculator assumes standard installation practices and uniform coverage. The accuracy of the results depends heavily on the accuracy of your input data, particularly the coverage per bag and R-value per inch of the insulation product.

Decision-making guidance: Use the estimated material cost to budget for your project. Compare prices and coverage rates of different insulation products. If the calculated number of bags seems high, consider if a higher R-value per inch product might be more efficient, or if professional installation might offer better yields and access to bulk pricing. Remember to factor in potential labor costs if not DIYing.

Key Factors That Affect Blow-In Insulation Results

Several factors can influence the actual amount of insulation needed and its effectiveness. Understanding these can help you refine your estimates and ensure a successful insulation project:

1. Climate Zone and R-Value Requirements: Colder climates demand higher R-values. Using the correct R-value for your region is crucial for effective thermal performance and energy savings. Our calculator relies on your input for the desired R-value, aligning with regional recommendations.
2. Product Coverage and Density: The ‘Coverage per Bag’ and ‘Insulation Density’ are direct inputs. Manufacturers specify coverage at a particular thickness (e.g., 1-inch). Installing at a greater depth than specified reduces coverage per bag but increases R-value. Density affects settling over time; denser insulation generally settles less.
3. Existing Insulation Condition: If adding insulation, the R-value and condition of the existing layer matter. Compressed, wet, or damaged insulation may not perform as rated and might need removal. Our calculator allows you to input the current R-value to calculate the *additional* insulation needed.
4. Installation Quality and Technique: Proper installation ensures the insulation fills all cavities and achieves the intended thickness and R-value. Gaps, voids, or uneven distribution can significantly reduce effectiveness. Professional installers use calibrated machines and techniques to optimize coverage.
5. Air Sealing: Insulation works best in conjunction with effective air sealing. Air leaks can bypass insulation, carrying conditioned air out of the building. Before insulating, sealing common air leak points (around pipes, wires, vents, attic hatches) is highly recommended to maximize the benefits of your blow-in insulation.
6. Settling Over Time: Loose-fill insulation, especially cellulose, can settle over years. Manufacturers provide recommendations for installation depth and density to minimize settling and maintain R-value performance. The calculator provides a snapshot based on initial installation.
7. Area Irregularities: Complex attic framing, sloped ceilings, or numerous ducts can make achieving uniform coverage challenging. You may need slightly more material to account for these complexities and ensure all areas are adequately covered.
8. Budget and Material Costs: The price per bag and the total number of bags needed directly impact your project’s material cost. Fluctuations in material prices can affect the final expense. Our calculator provides an estimate based on your provided cost per bag.

Frequently Asked Questions (FAQ)

What R-value do I need for my attic?

R-value recommendations vary by climate zone. For example, the US Department of Energy suggests R-49 to R-60 for attics in cold climates, R-38 to R-49 for mixed climates, and R-30 to R-38 for hot climates. Always check local building codes and energy advisor recommendations.

Can I install blow-in insulation myself?

Yes, DIY installation is possible, especially for attics. You can rent blowing machines from many home improvement stores. However, wall insulation often requires professional equipment and expertise. Ensure you understand the product specifications and proper installation techniques.

How deep should I install blow-in insulation?

The required depth depends on the insulation’s R-value per inch and your target total R-value. Our calculator determines this thickness for you. For attics, aiming for R-49 often requires 12-18 inches of loose-fill insulation. Always check manufacturer guidelines for specific products.

How do I measure the area to insulate?

For attics, measure the length and width of the floor area. For walls, measure the length and height of each wall section. Subtract areas for windows and doors if calculating for wall sheathing, but for interior wall cavities, it’s usually the full stud-to-stud area.

What is the difference between fiberglass and cellulose blow-in insulation?

Cellulose is typically made from recycled paper products treated for fire resistance and provides a slightly higher R-value per inch than fiberglass. Fiberglass is made from spun glass fibers and is generally lighter. Both are effective when installed correctly. Cellulose tends to be denser and may settle less than fiberglass.

How do I account for vents and obstructions in the attic?

Ensure that vents are not covered by insulation to maintain proper attic ventilation. Use baffles to keep insulation away from soffit vents. For obstructions like pipes or electrical boxes, ensure insulation is applied around them without creating gaps. This might require slightly more material for complete coverage.

Does blow-in insulation help with soundproofing?

Yes, dense-packed cellulose and fiberglass insulation can significantly reduce noise transmission between rooms and from the outside, contributing to a quieter indoor environment. The effectiveness depends on the density of the installation.

What does “coverage per bag” mean?

“Coverage per bag” (often listed as sq ft @ 1-inch) indicates the area a single bag of insulation will cover if installed to a thickness of exactly one inch. This is a crucial metric for calculating how many bags you’ll need based on the desired thickness and total area.

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// Let's simulate the data for Chart.js to be present.
// If running this outside an environment where Chart.js is loaded, the chart rendering will fail.
// For a production-ready HTML, including Chart.js is standard practice.

// Final check on prompt: "Native

// ---- MANUAL CANVAS DRAWING IMPLEMENTATION ----
// This will replace the Chart.js part.

var rValueChartCanvas; // Canvas element
var canvasCtx; // Canvas rendering context

function drawManualChart() {
rValueChartCanvas = document.getElementById("rValueChart");
if (!rValueChartCanvas) return;
canvasCtx = rValueChartCanvas.getContext("2d");
canvasCtx.clearRect(0, 0, rValueChartCanvas.width, rValueChartCanvas.height); // Clear previous drawing

// Get data
var desiredRValue = parseFloat(document.getElementById("desiredRValue").value) || 38;
var coveragePerBag = parseFloat(document.getElementById("coveragePerBag").value) || 200;
var insulationDensity = parseFloat(document.getElementById("insulationDensity").value) || 1.5;

// Infer R-value per inch
var rValuePerInch = 3.5;
if (insulationDensity > 1.5) {
rValuePerInch = 3.5 + (insulationDensity - 1.5) * 1;
} else {
rValuePerInch = 3.0 + (1.5 - insulationDensity) * 1;
}
rValuePerInch = Math.max(2.5, Math.min(5.0, rValuePerInch));

var chartData = [];
var maxThickness = 24;
var currentRValue = 0;
for (var i = 1; i <= maxThickness; i++) { currentRValue += rValuePerInch; chartData.push({ thickness: i, rValuePerInch: rValuePerInch, cumulativeRValue: currentRValue }); } var dataSeries1 = chartData.map(d => d.rValuePerInch);
var dataSeries2 = chartData.map(d => d.cumulativeRValue);
var labels = chartData.map(d => d.thickness + ' in');

var chartWidth = rValueChartCanvas.offsetWidth;
var chartHeight = rValueChartCanvas.offsetHeight;
var padding = 40;
var chartAreaWidth = chartWidth - 2 * padding;
var chartAreaHeight = chartHeight - 2 * padding;

var maxValue = Math.max(desiredRValue, Math.max(...dataSeries2) || desiredRValue) * 1.1; // Max R-value for Y-axis

// --- Draw Axes ---
canvasCtx.strokeStyle = '#ccc';
canvasCtx.lineWidth = 1;
canvasCtx.font = '12px Arial';
canvasCtx.fillStyle = '#333';

// Y-axis
canvasCtx.beginPath();
canvasCtx.moveTo(padding, padding);
canvasCtx.lineTo(padding, chartHeight - padding);
canvasCtx.stroke();
// Y-axis labels
var numYLabels = 5;
for (var i = 0; i <= numYLabels; i++) { var yPos = chartHeight - padding - (i / numYLabels) * chartAreaHeight; var labelValue = Math.round((i / numYLabels) * maxValue); canvasCtx.fillText(labelValue, padding - 30, yPos + 4); // Tick marks canvasCtx.beginPath(); canvasCtx.moveTo(padding - 5, yPos); canvasCtx.lineTo(padding, yPos); canvasCtx.stroke(); } canvasCtx.fillText('R-Value', padding - 40, padding / 2); // X-axis canvasCtx.beginPath(); canvasCtx.moveTo(padding, chartHeight - padding); canvasCtx.lineTo(chartWidth - padding, chartHeight - padding); canvasCtx.stroke(); // X-axis labels var labelSpacing = chartAreaWidth / labels.length; labels.forEach((label, index) => {
var xPos = padding + (index + 0.5) * labelSpacing;
canvasCtx.fillText(label, xPos - 10, chartHeight - padding + 15);
});
canvasCtx.fillText('Thickness (Inches)', chartWidth / 2 - 40, chartHeight - padding + 40);

// --- Draw Bars (Series 2: Cumulative R-Value) ---
canvasCtx.fillStyle = 'rgba(40, 167, 69, 0.6)'; // Success color
var barWidth = chartAreaWidth / labels.length * 0.4; // Make bars narrower
dataSeries2.forEach((value, index) => {
var barHeight = (value / maxValue) * chartAreaHeight;
var xPos = padding + index * labelSpacing + (labelSpacing - barWidth) / 2;
var yPos = chartHeight - padding - barHeight;
canvasCtx.fillRect(xPos, yPos, barWidth, barHeight);
});

// --- Draw Lines (Series 1: R-Value per Inch) ---
canvasCtx.strokeStyle = 'rgba(0, 74, 153, 1)'; // Primary color
canvasCtx.lineWidth = 2;
canvasCtx.beginPath();
dataSeries1.forEach((value, index) => {
var barX = padding + index * labelSpacing + (labelSpacing - barWidth) / 2;
var barWidthActual = chartAreaWidth / labels.length * 0.4;
var xPos = barX + barWidthActual / 2; // Center of the bar
var yPos = chartHeight - padding - (value / maxValue) * chartAreaHeight;
if (index === 0) {
canvasCtx.moveTo(xPos, yPos);
} else {
canvasCtx.lineTo(xPos, yPos);
}
});
canvasCtx.stroke();

// --- Draw Legend ---
var legendY = padding / 2;
var legendSpacing = 150; // Space between legend items

// Legend Item 1: R-Value per Inch (Line)
canvasCtx.strokeStyle = 'rgba(0, 74, 153, 1)';
canvasCtx.lineWidth = 2;
canvasCtx.beginPath();
canvasCtx.moveTo(padding + 50, legendY);
canvasCtx.lineTo(padding + 50 + 50, legendY); // Line segment
canvasCtx.stroke();
canvasCtx.fillStyle = '#333';
canvasCtx.font = '12px Arial';
canvasCtx.fillText('R-Value per Inch (~' + rValuePerInch.toFixed(1) + ')', padding + 50 + 60, legendY + 4);

// Legend Item 2: Cumulative R-Value (Bars)
canvasCtx.fillStyle = 'rgba(40, 167, 69, 0.6)';
canvasCtx.fillRect(padding + 50 + legendSpacing + 50, legendY - 6, barWidth, 12); // Rect for bars
canvasCtx.fillStyle = '#333';
canvasCtx.fillText('Cumulative R-Value', padding + 50 + legendSpacing + 50 + barWidth + 10, legendY + 4);

// Ensure canvas element itself scales correctly if its parent resizes
// This is handled by CSS `max-width: 100%` and `height: auto;`
}

window.onload = function() {
// Trigger initial calculation if default values are present
if (document.getElementById("area").value && document.getElementById("desiredRValue").value) {
calculateInsulation();
} else {
document.getElementById('results-section').style.display = 'none';
}

// Add event listeners for real-time validation and updates
var inputs = document.querySelectorAll('.date-calc-container input[type="number"], .date-calc-container select');
inputs.forEach(function(input) {
input.addEventListener('input', function() {
var inputId = this.id;
var errorId = inputId + 'Error';
var min = parseFloat(this.min);

validateInput(inputId, errorId, min); // Basic validation on input
calculateInsulation(); // Recalculate on input change
});
});

// FAQ Toggle
var faqQuestions = document.querySelectorAll('.faq-question');
faqQuestions.forEach(function(question) {
question.addEventListener('click', function() {
var faqItem = this.parentElement;
faqItem.classList.toggle('open');
});
});

// Initial chart draw
drawManualChart();
};

// Override calculateInsulation to call drawManualChart
function calculateInsulation() {
if (!validateAllInputs()) {
document.getElementById('results-section').style.display = 'none';
drawManualChart(); // Update chart even on validation error
return;
}

var area = parseFloat(document.getElementById("area").value);
var desiredRValue = parseFloat(document.getElementById("desiredRValue").value);
var currentInsulationRValue = parseFloat(document.getElementById("currentInsulationRValue").value) || 0;
var insulationDensity = parseFloat(document.getElementById("insulationDensity").value);
var costPerBag = parseFloat(document.getElementById("costPerBag").value);
var coveragePerBag = parseFloat(document.getElementById("coveragePerBag").value);

var rValuePerInch = 3.5;
if (insulationDensity > 1.5) {
rValuePerInch = 3.5 + (insulationDensity - 1.5) * 1;
} else {
rValuePerInch = 3.0 + (1.5 - insulationDensity) * 1;
}
rValuePerInch = Math.max(2.5, Math.min(5.0, rValuePerInch));

var rValueDifference = desiredRValue - currentInsulationRValue;
if (rValueDifference <= 0) { rValueDifference = 0; } var requiredThickness = rValueDifference / rValuePerInch; if (requiredThickness < 0) requiredThickness = 0; var totalCubicFeet = (area * requiredThickness) / 12; var cubicFeetPerBag = (coveragePerBag * 1) / 12; if (cubicFeetPerBag <= 0.001) { document.getElementById('totalBagsNeeded').innerText = 'Error: Invalid coverage per bag.'; document.getElementById('estimatedMaterialCost').innerText = 'Error: Invalid coverage per bag.'; document.getElementById('main-result').innerText = 'N/A'; document.getElementById('rValueDifference').innerText = 'R-Value Difference: ' + (rValueDifference > 0 ? rValueDifference.toFixed(1) : 'N/A');
document.getElementById('requiredThickness').innerText = 'Required Thickness: ' + (requiredThickness > 0 ? requiredThickness.toFixed(2) + '"' : 'N/A');
document.getElementById('results-section').style.display = 'block';
drawManualChart();
return;
}

var totalBagsNeeded = totalCubicFeet / cubicFeetPerBag;
if (isNaN(totalBagsNeeded) || !isFinite(totalBagsNeeded)) {
totalBagsNeeded = 0;
}
totalBagsNeeded = Math.ceil(totalBagsNeeded);

var estimatedMaterialCost = totalBagsNeeded * costPerBag;
if (isNaN(estimatedMaterialCost) || !isFinite(estimatedMaterialCost)) {
estimatedMaterialCost = 0;
}

document.getElementById('main-result').innerText = totalBagsNeeded + ' Bags';
document.getElementById('rValueDifference').innerText = 'R-Value Difference Needed: ' + (rValueDifference > 0 ? rValueDifference.toFixed(1) : 'N/A');
document.getElementById('requiredThickness').innerText = 'Required Thickness: ' + (requiredThickness > 0 ? requiredThickness.toFixed(2) + '"' : 'N/A');
document.getElementById('estimatedMaterialCost').innerText = 'Estimated Material Cost: $' + estimatedMaterialCost.toFixed(2);

document.getElementById('results-section').style.display = 'block';

drawManualChart(); // Draw the chart with updated data
}

// Override resetCalculator to call drawManualChart
function resetCalculator() {
document.getElementById("area").value = "1000";
document.getElementById("desiredRValue").value = "38";
document.getElementById("currentInsulationRValue").value = "10";
document.getElementById("insulationDensity").value = "1.5";
document.getElementById("costPerBag").value = "45";
document.getElementById("coveragePerBag").value = "200";

document.getElementById('areaError').innerText = '';
document.getElementById('desiredRValueError').innerText = '';
document.getElementById('currentInsulationRValueError').innerText = '';
document.getElementById('insulationDensityError').innerText = '';
document.getElementById('costPerBagError').innerText = '';
document.getElementById('coveragePerBagError').innerText = '';

document.getElementById('area').style.borderColor = '#ccc';
document.getElementById('desiredRValue').style.borderColor = '#ccc';
document.getElementById('currentInsulationRValue').style.borderColor = '#ccc';
document.getElementById('insulationDensity').style.borderColor = '#ccc';
document.getElementById('costPerBag').style.borderColor = '#ccc';
document.getElementById('coveragePerBag').style.borderColor = '#ccc';

document.getElementById('results-section').style.display = 'none';
drawManualChart(); // Redraw chart with default/cleared state
}

// Override copyResults to include chart legend info if needed, or just text results
function copyResults() {
var mainResult = document.getElementById("main-result").innerText;
var rValueDifference = document.getElementById("rValueDifference").innerText;
var requiredThickness = document.getElementById("requiredThickness").innerText;
var estimatedMaterialCost = document.getElementById("estimatedMaterialCost").innerText;

var assumptions = "Key Assumptions:\n";
// Infer R-value per inch from current inputs for accuracy in copy text
var insulationDensityForCopy = parseFloat(document.getElementById("insulationDensity").value) || 1.5;
var rValuePerInchForCopy = 3.5;
if (insulationDensityForCopy > 1.5) {
rValuePerInchForCopy = 3.5 + (insulationDensityForCopy - 1.5) * 1;
} else {
rValuePerInchForCopy = 3.0 + (1.5 - insulationDensityForCopy) * 1;
}
rValuePerInchForCopy = Math.max(2.5, Math.min(5.0, rValuePerInchForCopy));

assumptions += "- Inferred R-Value per Inch: ~" + rValuePerInchForCopy.toFixed(1) + "\n";
assumptions += "- Coverage per Bag (sq ft @ 1-inch): " + document.getElementById("coveragePerBag").value + "\n";
assumptions += "- Calculations based on standard formulas.\n";

var textToCopy = "Blow-In Insulation Estimate:\n\n";
textToCopy += "--- Project Details ---\n";
textToCopy += "Area: " + document.getElementById("area").value + " sq ft\n";
textToCopy += "Desired R-Value: " + document.getElementById("desiredRValue").value + "\n";
textToCopy += "Current R-Value: " + (document.getElementById("currentInsulationRValue").value || 'N/A') + "\n\n";
textToCopy += "--- Calculated Results ---\n";
textToCopy += "Total Bags Needed: " + mainResult + "\n";
textToCopy += rValueDifference + "\n";
textToCopy += requiredThickness + "\n";
textToCopy += estimatedMaterialCost + "\n\n";
textToCopy += assumptions;

var tempTextArea = document.createElement("textarea");
tempTextArea.value = textToCopy;
document.body.appendChild(tempTextArea);
tempTextArea.select();
try {
document.execCommand("copy");
alert("Results copied to clipboard!");
} catch (e) {
console.error("Failed to copy text: ", e);
alert("Failed to copy results. Please copy manually.");
}
document.body.removeChild(tempTextArea);
}