To find how many bags of cellulose insulation your attic needs, divide your attic floor area by the coverage per bag for your target R-value. That coverage is printed on the bag chart. For one common 30-pound cellulose product, R-49 covers about 16.5 square feet per bag. That’s about 60 bags per 1,000 square feet, …

R25 insulation is about 8 inches thick as a fiberglass batt, about 7 inches as blown cellulose and about 10 inches as blown fiberglass. Closed cell spray foam reaches R25 in about 4 inches. R25 is a good fit for floors over garages and crawl spaces, where it fills a 2×8 or 2×10 joist bay. …

A home inspector pushes a ruler into the attic of a Denver ranch house and reads about 11 inches of gray cellulose. The seller’s paperwork says the attic was brought up to R-38 a few years ago. The buyer wants to know if that number is good enough or a project waiting to happen. The …