Insulation R-Value Calculator
Find the recommended R-value for your project, calculate your current R-value, and estimate the additional depth of material required.
Recommended Total Insulation
Additional needed: R-29
Add: 7.8 inches
Understanding Insulation R-Values
An insulation's **R-value** measures its resistance to conductive heat flow. The higher the R-value, the better the thermal performance. Standard requirements vary depending on where you live (US Climate Zones) and the section of the house being insulated.
R-Value per Inch of Material
The R-value of insulation is determined by its thickness. Here are the R-values per inch for standard thermal materials:
- Closed-Cell Spray Foam: **R-6.0 to R-6.5 per inch**. Most efficient, blocks air leaks, but expensive.
- Blown-in Cellulose: **R-3.2 to R-3.8 per inch**. Recycled newspaper fiber treated with fire retardant; popular for attics.
- Fiberglass Batts/Rolls: **R-2.9 to R-3.8 per inch**. Traditional pink glass fiber batts. Easy DIY.
- Blown-in Fiberglass: **R-2.2 to R-2.8 per inch**. Loose-fill fiberglass blown into attics.
Attic vs. Wall Insulation Guidelines
Because warm air rises, heat loss is highest through the roof. Energy Star guidelines recommend **R-38 to R-60** for attics in cold climates, compared to **R-13 to R-21** for exterior framing walls which have limited cavity space.