Insulation Calculator
Calculates batts, rolls, or blown-in insulation needed by R-value and area
Total square footage to insulate
Type of insulation material
Target thermal resistance value
Select all options to see material estimate
Required insulation thickness
Approximate material cost
Frequently Asked Questions
What R-value do I need?
R-value requirements vary by climate zone and building element. Attics in cold climates need R-49 to R-60. Exterior walls typically need R-13 to R-21. Floors over unconditioned spaces need R-25 to R-30. Check your local building code for specific requirements.
What type of insulation is best?
Fiberglass batts are the most affordable and easiest to install in open framing. Blown-in cellulose fills irregular cavities and adds density. Spray foam provides the highest R-value per inch and creates an air barrier. Each type suits different applications and budgets.
How thick does insulation need to be?
Thickness depends on the type and target R-value. Fiberglass batts need about 3.5 inches for R-13 and 6.25 inches for R-19. Blown cellulose needs about 3.5 inches per R-13. Closed-cell spray foam achieves R-13 in just 2 inches because of its higher R-value per inch.
Can I add insulation over existing insulation?
Yes, you can add unfaced insulation over existing insulation in attics to increase the R-value. Do not add faced insulation on top because the vapor barrier can trap moisture. Blown-in insulation works especially well for topping off attic insulation.
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