Attic Insulation R-Values by Climate Zone
ENERGY STAR gives an R-value range for each climate zone: for an uninsulated attic the lowest figure is 30[1] and the highest is 60[1], and an attic that already has insulation uses a lower range.
Estimates for planning, not professional advice. Read the full notice.
Attic R-values by climate zone
The R-value ranges ENERGY STAR lists for an attic, by climate zone, for an uninsulated attic and for an attic with insulation already there
| Climate zone | Uninsulated attic, from R | Uninsulated attic, to R | Insulation already there, from R | Insulation already there, to R |
|---|---|---|---|---|
| Zone 1 | 30 | 49 | 25 | 30 |
| Zone 2 | 30 | 60 | 25 | 38 |
| Zone 3 | 30 | 60 | 25 | 38 |
| Zone 4 | 38 | 60 | 38 | 38 |
| Zones 5 to 8 | 49 | 60 | 38 | 49 |
Source: [1]
A zone with one figure in the source, such as the fourth zone with insulation already there, shows the same figure in both columns. The source page carries no date, so the table says what it said on the day it was checked.
R-value of insulation by depth
The total R-value of a layer by its depth in inches and its kind, from the R per inch ENERGY STAR gives for each kind
| Depth | Loose fiberglass | Loose rock wool | Loose cellulose | Fiberglass batts |
|---|---|---|---|---|
| 4 in | 10 | 11.2 | 14.8 | 12.8 |
| 6 in | 15 | 16.8 | 22.2 | 19.2 |
| 8 in | 20 | 22.4 | 29.6 | 25.6 |
| 10 in | 25 | 28 | 37 | 32 |
| 12 in | 30 | 33.6 | 44.4 | 38.4 |
| 14 in | 35 | 39.2 | 51.8 | 44.8 |
| 16 in | 40 | 44.8 | 59.2 | 51.2 |
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Each figure is the depth times the R per inch of the kind. The R per inch values are ENERGY STAR's, listed in the sources, and a real layer can differ.
R per inch of the kinds in the second table
Loose fibers: light-weight yellow, pink, or white fiberglass =2.5 x depth dense gray or near white, may have black specs rock wool =2.8 x depth small gray flat pieces or fibers (from newsprint) cellulose =3.7 x depth
Batts: light-weight yellow, pink, or white fiberglass =3.2 x depth
Questions
What is the R-value of 10 inches of insulation?
Multiply the depth in inches by the R per inch of the kind. The second table gives the result for a ten-inch layer of each kind ENERGY STAR lists, and the insulation calculator takes the R already there off your target.
Which climate zone am I in?
The ENERGY STAR page this chart comes from shows a climate zone map. Find your county on it, then read the row for your zone.
How do I get from an R-value to bags or batts?
Open the insulation calculator with your attic's size and target R-value. It takes the existing R off the target, finds the chart row that reaches the rest and counts the bags.
Calculate it for your project
Enter your own sizes to get the amount to buy or the layout figures, with the working shown and a page to print.
Open the insulation calculatorSources (1)
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What to Look For: DIY Checks and Inspections (opens in new tab), ENERGY STAR (U.S. Environmental Protection Agency and Department of Energy), web page, undated.
Code or government.
“Add the following insulation levels to your attic For uninsulated attics For attics with existing 3−4 inches of insulation … 1 R30 to R49 R25 to R30”
“Add the following insulation levels to your attic For uninsulated attics For attics with existing 3−4 inches of insulation … 2 R30 to R60 R25 to R38”
“Loose fibers: light-weight yellow, pink, or white fiberglass =2.5 x depth dense gray or near white, may have black specs rock wool =2.8 x depth small gray flat pieces or fibers (from newsprint) cellulose =3.7 x depth”
“Batts: light-weight yellow, pink, or white fiberglass =3.2 x depth”
“Add the following insulation levels to your attic For uninsulated attics For attics with existing 3−4 inches of insulation … 3 R30 to R60 R25 to R38”
“Add the following insulation levels to your attic For uninsulated attics For attics with existing 3−4 inches of insulation … 4 R38 to R60 R38”
“Add the following insulation levels to your attic For uninsulated attics For attics with existing 3−4 inches of insulation … 5 to 8 R49 to R60 R38 to R49”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1)
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.