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Bags, depth, air sealing and installation priced to reach your target R-value.
Common US attics, blown-in fiberglass.
Tap a preset in the calculator above to load a typical job, then adjust the numbers to match your site.
Starting points: 1,200 sq ft, R-11 to R-49 · 1,200 sq ft, R-19 to R-49 · 1,200 sq ft, R-11 to R-38 · 2,000 sq ft, R-11 to R-49 · 1,200 sq ft to R-60
See installed prices and permit rules for attic insulation r-value calculator.
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Measure the attic, check the current R-value, then top up to the target depth.
R-49 to R-60 for most US climates under IECC 2021, and R-38 in milder zones. A typical existing attic has R-11 to R-19, so a top-up is usually worthwhile.
Divide the area by the bag coverage for your target R-value. For blown fiberglass at about 520 sq ft-R per bag, a 1,200 sq ft attic going from R-11 to R-49 needs about 57 bags.
About 14 to 18 inches for R-49 with blown fiberglass. Depth is what delivers the R-value, so do not compress it.
The DOE estimates air sealing plus insulation can cut heating and cooling costs by around 10 to 20 percent. Air sealing usually carries the bigger share.
Home centers rent blowers and it is a realistic DIY job with two people. The attic must be air sealed first, and safety gear is essential.
Utility programs frequently offer rebates per square foot of insulation. Check your utility and keep the product labels and invoice.
Using the calculator defaults, 1,200 sq ft, r-11 to r-49 gives Bags of blown-in: 88 and Typical cost: $2,309, with a typical range $1,636 to $3,165. Change the waste allowance, material or thickness to match your site.
Using the calculator defaults, 1,200 sq ft to r-60 gives Bags of blown-in: 114 and Typical cost: $2,777, with a typical range $1,948 to $3,841. Change the waste allowance, material or thickness to match your site.