Calculator Inputs
Example Data Table
| Project | Area | Existing R | Target R | R Per Inch | Added Depth | Notes |
|---|---|---|---|---|---|---|
| Small attic top-up | 650 sq ft | 19 | 49 | 3.7 | About 8.11 in | Good for a quick upgrade. |
| Medium attic | 1,000 sq ft | 13 | 49 | 3.7 | About 9.73 in | Check vent chutes first. |
| Large attic | 1,800 sq ft | 11 | 60 | 3.7 | About 13.24 in | Plan staging and access. |
Formula Used
Net fill area = Gross area × (1 − obstruction percentage)
Settled depth from R target = (Target R − Existing R) ÷ R per inch
Planned blow depth = Settled depth ÷ (1 − settling allowance)
Coverage at chosen depth = Reference coverage × Reference depth ÷ planned blow depth
Bags needed = Ceiling((Net area ÷ coverage at chosen depth) × (1 + waste percentage))
Total cost = Material cost + machine rental + delivery + labor + tax
How To Use This Calculator
- Enter the attic or cavity area directly, or use length and width.
- Add obstruction deduction for chimneys, platforms, shafts, or blocked spaces.
- Choose target R mode for code planning, or manual depth mode.
- Enter the coverage from the insulation bag label.
- Add waste, cost, labor, delivery, tax, and machine rental.
- Press calculate and review bags, depth, cost, volume, and density.
- Download the result as a CSV or PDF file.
Green Fiber Blown Insulation Planning Guide
Why Accurate Bag Planning Matters
Blown insulation projects look simple at first. Yet small errors can change the final cost. A shallow layer may miss the required thermal target. A heavy layer can waste bags and money. This calculator helps you plan depth, coverage, bags, and total budget before work begins.
Measure The Area First
Start with a clean area measurement. Use direct square footage when you already know it. Use length and width when the attic has a basic rectangle shape. Deduct blocked zones carefully. Do not remove too much area. Most attics still need extra material around joists and edges.
Use The Bag Label
Every loose fill product has a coverage chart. That chart is very important. It connects bags, depth, settled thickness, coverage, and density. Enter the reference coverage and reference depth from the label. The calculator then scales coverage for your chosen depth. This gives a practical material estimate.
Plan For Settling And Waste
Loose fill may settle after installation. The settling field helps you plan a deeper initial blow. Waste is also normal. Access problems, uneven framing, wind wash areas, and machine changes can increase usage. A small overage helps avoid a short purchase during installation.
Review Costs Before Buying
The cost result includes bags, labor, rental, delivery, and tax. It also shows cost per square foot. This makes quotes easier to compare. It also helps homeowners decide whether to install the material themselves or hire a crew. Always check local code, ventilation, moisture, and air sealing needs first.
FAQs
1. What does this blown insulation calculator estimate?
It estimates depth, coverage, bag count, material cost, labor cost, total cost, weight, volume, and final R value for loose fill insulation projects.
2. Can I use this for attic insulation?
Yes. It is mainly designed for attic top-up and open cavity planning. Always confirm access, ventilation, and air sealing before installation.
3. Where do I find bag coverage values?
Use the coverage chart printed on the insulation bag or manufacturer document. Enter the listed coverage and the matching reference depth.
4. Why does the calculator include settling?
Loose fill can settle after installation. The settling allowance helps estimate a higher initial blow depth to reach the intended settled depth.
5. Should I include waste percentage?
Yes. Waste covers uneven framing, access limits, machine variation, and installer handling. Many projects use a modest overage for safety.
6. Is the final bag count exact?
No. It is an estimate. Final use depends on actual product density, hose setup, weather, joist layout, and installer technique.
7. Can this replace local building code advice?
No. Use it for planning only. Confirm required R values, ventilation rules, fire clearances, and moisture control with local guidance.
8. Why is density shown in the result?
Density helps compare the estimate with product guidance. Very low or high density may mean the coverage inputs need review.