How much insulation do you need?
Pick where and your climate zone, add the area, get the R-value and bags instantly.
How do I calculate how much insulation I need?
Find the area to insulate — for an attic, the length times the width of the attic floor — and divide by the square feet one bag or roll covers at the R-value you want; that figure is printed on the label. A 30 by 40 ft attic is 1,200 square feet; with 10% extra and bags that cover 40 square feet, that is 33 bags.
What R-value do I need in my attic?
ENERGY STAR recommends R-30 for an uninsulated attic in climate zone 1, R-49 in zones 2 and 3, and R-60 in zones 4 through 8. If the attic already has 3 to 4 inches of insulation, add R-25 in zone 1, R-38 in zones 2 and 3, and R-49 from zone 4 north.
What insulation goes in 2×4 and 2×6 walls?
A 2×4 wall has a 3½ inch cavity, which takes R-13 or R-15 batts; a 2×6 wall has 5½ inches, for R-19 or R-21. In an existing house, the cavities can also be filled with blown-in insulation, and ENERGY STAR suggests adding insulated sheathing under new siding in zones 3 and colder.
How many bags of blown-in insulation do I need?
Every bag of loose-fill insulation has a chart that lists how many square feet it covers — and how deep to blow it — for each R-value. Enter that coverage for your target R and the calculator counts the bags. The deeper the target, the fewer square feet per bag.
Which climate zone am I in?
The US is split into zones 1 through 8 from the warmest to the coldest, as used by the building codes. South Florida and Hawaii are zone 1, most of the Southeast is zone 3, the Mid-Atlantic is zone 4, the Northeast and Great Lakes are zone 5, the upper Midwest is zone 6 and interior Alaska is zone 8. Your county's zone is listed in the IECC energy code.