Blown Insulation Coverage
The bags of blown insulation an attic needs at a target R.
Example
You enter
- Attic area (sq ft) 1200
- Bags per 1,000 sq ft 36
- R per inch 3.5
- Target R-value 38
You get
- Bags 44
- Min settled thickness 10.9 in
Checked against published worked examples from: CertainTeed Corporation.
Details, formula, and sources
ScopeFrom the area and the manufacturer's bags-per-1,000-sq-ft figure, with the minimum installed (settled) thickness.
Formula or tableBags = ceil(area / 1000 x bags per 1,000); coverage per bag = 1000 / bags-per-1000; minimum thickness = target R / R-per-inch.
Source and editionManufacturer blown-insulation coverage charts (by name).
Free accessCoverage charts free on the insulation bag and the maker's pages.
What governsEstimate. AHJ and licensed professional govern.
API field namesarea_sqft, bags_per_1000, r_per_inch, target_r, bags, min_thickness_in
- R per inch ~3.5 cellulose, ~2.5 blown fiberglass (editable); read the bag's settled-thickness columninsulation maker charts