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HeizerDesk Insulation Calculator
Pick the insulation type and the R-value you are aiming for. This returns how deep it has to be, and how much material that is for your square footage. A free insulation calculator you can use on the job: nothing to install, nothing to register.
Your numbers
Result
Depth required
19.6
inches
- Bags or bundles
- 30bags
- R-value to add
- 49R
- Finished R-value
- 49R
- Area covered
- 1,200sq ft
- Board feet of foamHow spray foam is quoted
- 23,520bd ft
How this is calculated
- R-value to add = target R − existing R.
- Depth = R-value to add ÷ R-value per inch of the material.
- Bags = area ÷ coverage per bag at that depth.
- Board feet = area × depth in inches - the unit spray foam is priced in.
Before you order
- Coverage per bag is not a constant. Every blown-insulation bag has a chart on it giving coverage at each depth, and deeper means fewer square feet per bag - use the number for YOUR depth.
- Batts only reach their rated R-value if they fill the cavity without being compressed. An R-19 batt squashed into a 2x4 wall does not perform as R-19.
- Do not bury recessed lights, bath fans or a chimney without checking clearances first. Non-IC-rated fixtures are a fire risk when covered.
- Attic ventilation has to keep working. Baffles at the eaves stop blown insulation from blocking the soffit vents.