How the insulation calculator works
Enter the square footage of the wall, floor, or attic you want to insulate and pick your product. Each product has a coverage rate per bag or roll; we divide your area (plus a waste factor for trims) by that coverage to get the number of units, then multiply by a typical price for a cost estimate.
Which R-value do I need?
R-value measures resistance to heat flow — higher is warmer. As a rule of thumb: R-13 to R-15 for 2x4 exterior walls, R-19 to R-21 for 2x6 walls, and R-30 to R-49 for attics depending on climate zone. Colder climates need more. Check your local energy code for the required minimum.
Batts vs. blown-in — which is better?
Batts are cheapest and easy for open stud bays and DIY. Blown-in fills irregular spaces and existing attics with fewer gaps, but needs a machine (often free with material purchase). For a new open wall, batts win on cost; for an existing attic, blown-in usually wins on coverage.
Do I include the waste factor?
Yes — always order 10–15% extra for offcuts around outlets, pipes, and awkward bays. Running short means a second trip to the supply house.