Attic Insulation Calculator (Blown-In)
Depth and bags of blown-in cellulose to reach a target R-value over what's already there.
Check the bag's own coverage chart at your R — settled density rules. Air-seal top plates and can lights BEFORE burying them; insulation doesn't stop airflow, it just hides the leaks.
Formula
Attic Insulation Calculator (Blown-In) is a free attic insulation calculator for civil engineers, contractors and quantity surveyors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Attic Insulation Calculator (Blown-In)
Depth and bags of blown-in cellulose to reach a target R-value over what's already there. The calculation implements depth = (R_target − R_existing) ÷ R-per-inch; cellulose settles ≈ 24 kg/m³ (DOE Insulation Fact Sheet; CIMA cellulose coverage). Check the bag's own coverage chart at your R — settled density rules. Air-seal top plates and can lights BEFORE burying them; insulation doesn't stop airflow, it just hides the leaks.
How to use Attic Insulation Calculator (Blown-In)
- 1Enter Attic area in m².
- 2Enter Target R-value (imperial) (DOE: R-38 most climates, R-49 cold).
- 3Enter Existing R-value.
- 4Enter R per inch of material (Cellulose 3.5 · loose fiberglass 2.5).
- 5Read Added depth needed, 25 lb bags (cellulose), Material weight instantly — no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Attic Insulation Calculator (Blown-In)?
- ✓Implements the standard formula — depth = (R_target − R_existing) ÷ R-per-inch; cellulose settles ≈ 24 kg/m³
- ✓Reference cited on-page: DOE Insulation Fact Sheet; CIMA cellulose coverage
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Attic Insulation Calculator (Blown-In) use?+
It computes depth = (R_target − R_existing) ÷ R-per-inch; cellulose settles ≈ 24 kg/m³, per DOE Insulation Fact Sheet; CIMA cellulose coverage. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
Check the bag's own coverage chart at your R — settled density rules. Air-seal top plates and can lights BEFORE burying them; insulation doesn't stop airflow, it just hides the leaks.
Does it include wastage?+
Yes — standard wastage/bulking factors are built in and stated in the formula line, so the quantity is an orderable number, not a bare geometric volume.
Is the Attic Insulation Calculator (Blown-In) free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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