Guides / Insulation · Updated
How many bags of AttiCat do you need?
Owens Corning AttiCat blown-in fiberglass, 27.5 lb bags. From Owens Corning's data sheet (May 2026).
Short answer
Find your R-value below, then divide your attic's square feet by the square feet per bag and round up.
| R-value | Depth (in) | Sq ft per bag (max) | Bags per 1,000 sq ft |
|---|---|---|---|
| R13 | 5 | 169.8 | 6 |
| R19 | 7 | 110.7 | 10 |
| R22 | 8 | 94.8 | 11 |
| R26 | 9.5 | 79.3 | 13 |
| R30 | 10.75 | 68.5 | 15 |
| R38 | 13.5 | 52.6 | 20 |
| R44 | 15.5 | 44.6 | 23 |
| R49 | 17 | 39.9 | 26 |
| R60 | 20.5 | 31.8 | 32 |
Owens Corning says AttiCat settling is negligible, so the depth you blow is the depth that counts. Their rule: the R-value is reached only with at least the chart's bags per 1,000 sq ft at no less than the chart's depth. Blow it thinner over more area and you don't get the R-value, even if it looks deep enough.
Bags for common attic sizes
| Attic floor | R30 | R38 | R49 | R60 |
|---|---|---|---|---|
| 600 sq ft | 9 | 12 | 16 | 19 |
| 800 sq ft | 12 | 16 | 21 | 26 |
| 1,000 sq ft | 15 | 20 | 26 | 32 |
| 1,200 sq ft | 18 | 23 | 31 | 38 |
| 1,500 sq ft | 22 | 29 | 38 | 48 |
| 2,000 sq ft | 30 | 39 | 51 | 63 |
Rounded up. Add a bag or two for the hatch, corners and mistakes.
Which R-value
ENERGY STAR recommends R30 in climate zone 1, R49 in zones 2 and 3, and R60 in zones 4 to 8. If there's already insulation up there, you add less: the attic insulation calculator finds your zone by ZIP, takes off what you have, and counts the bags.
Source: Owens Corning AttiCat data sheet. Compare brands in theattic insulation calculator.