Depth, bags, and R-value

Blown-in insulation FAQ

Turn attic measurements and product coverage charts into a defensible material estimate without guessing from depth alone.

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How Do I Use a Blown-In Insulation Calculator?
Use a blown-in insulation calculator by entering the attic area, existing insulation, target R-value, material, and exact bag coverage from the product label. The result should round up to a whole-bag count and show the minimum installed depth and weight needed for the added R-value.
What Is the R-Value per Inch of Blown-In Insulation?
Blown-in insulation is commonly around R-3 to R-3.5 per inch, with product-specific differences between cellulose, fiberglass, and mineral wool. Use that range only for an initial estimate; the manufacturer's coverage chart and installed-depth instructions determine the bag count for a real project.
Does Blown-In Insulation Have Asbestos?
Modern blown-in cellulose and fiberglass insulation are not asbestos insulation. The concern is older loose-fill vermiculite, which can resemble small gray, brown, or gold pebbles and may be contaminated with asbestos. Treat suspected vermiculite as hazardous and leave it undisturbed until a qualified professional advises you.

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