Insulation Thickness Chart: R-38 to R-60 by Material
By Marko VisicBSc Physics, University of Ljubljana
Codes and ENERGY STAR give R-values; your attic has a ruler. This chart turns one into the other for batts, blown-in fiberglass, cellulose and spray foam.
R-38 insulation is 12½ inches thick as an Owens Corning PINK Next Gen batt. Blown in, it takes 13½ inches of AttiCat fiberglass, or 11.2 inches of Greenfiber cellulose that settles to 10.4. Spray foam gets there thinner: about 10.3 inches of open-cell or 5.1 inches of closed-cell foam at Huntsman’s ratings.
12½in
R-38 as a fiberglass batt
Insulation thickness chart
Thickness depends on the material as much as the R-value. The batts are Owens Corning’s PINK Next Gen, the blown fiberglass its AttiCat, the cellulose Greenfiber’s SANCTUARY with the depth to blow it in and the depth it settles to, and the spray foams Huntsman’s at the R per inch it rates them.
| R-value | Batt | Blown fiberglass | Cellulose, blown / settled | Open-cell foam | Closed-cell foam |
|---|---|---|---|---|---|
| R-13 | 3½ in | 5 in | 3.9 / 3.6 in | 3.5 in | 1.8 in |
| R-19 | 6½ in | 7 in | 5.7 / 5.3 in | 5.1 in | 2.6 in |
| R-22 | 6¾ in | 8 in | 6.6 / 6.1 in | 5.9 in | 3 in |
| R-30 | 10 in | 10¾ in | 8.9 / 8.3 in | 8.1 in | 4.1 in |
| R-38 | 12½ in | 13½ in | 11.2 / 10.4 in | 10.3 in | 5.1 in |
| R-49 | 14 in | 17 in | 14.3 / 13.3 in | 13.2 in | 6.6 in |
| R-60 | no batt | 20½ in | 17.3 / 16.1 in | 16.2 in | 8.1 in |
R-38 insulation thickness
An R-38 PINK Next Gen batt is 12½ inches thick. Its R-38C batt is 10¼ inches: Owens Corning made it for cathedral ceilings, where a standard R-38 batt squeezed into the cavity with a vent baffle gave only about R-35, by its 2012 data sheet. Blown in, R-38 takes 13½ inches of AttiCat fiberglass, about 19 bags for every thousand square feet, or 11.2 inches of Greenfiber cellulose that settles to 10.4.
Spray foam reaches R-38 with less depth: 5.1 inches of closed-cell foam at R-7.4 per inch, or 10.3 inches of open-cell at R-3.7.
Attic insulation depth by climate zone
ENERGY STAR’s retrofit table, based on the 2021 IECC, gives an R-value for an attic with no insulation and one for an attic that already has three to four inches. The table below puts the first in inches of blown fiberglass and settled cellulose.
| Zone | Uninsulated attic | Blown fiberglass | Cellulose, settled | Add to existing | Floor |
|---|---|---|---|---|---|
| 1 | R-30 | 10¾ in | 8.3 in | R-25 | R-13 |
| 2 | R-49 | 17 in | 13.3 in | R-38 | R-13 |
| 3 | R-49 | 17 in | 13.3 in | R-38 | R-19 |
| 4A and 4B | R-60 | 20½ in | 16.1 in | R-49 | R-19 |
| 4C, 5 and 6 | R-60 | 20½ in | 16.1 in | R-49 | R-30 |
| 7 and 8 | R-60 | 20½ in | 16.1 in | R-49 | R-38 |
ENERGY STAR heads its attic columns as insulation to add, so with three to four inches already in place, add the R-value in the fifth column. Its floor column is the level for an insulated floor; crawl space walls have their own code levels in the crawl space encapsulation guide.
R-49 and R-60 insulation thickness
R-49 is 14 inches as a PINK Next Gen batt, the thickest on the sheet, 17 inches of AttiCat fiberglass, or 14.3 inches of cellulose blown in to settle at 13.3.
No batt on the sheet reaches R-60, so it is blown in or built from layers: 20½ inches of AttiCat fiberglass, about 31.5 bags for every thousand square feet, or 17.3 inches of cellulose that settles to 16.1. Either way the attic needs that much room below the roof deck and its vents.
Batt insulation thickness chart
Batts come in set thicknesses, and a higher R-value is not always thicker: the R-21 batt is 5½ inches, an inch less than the R-19 at 6½, and R-13 and R-15 are both 3½ inches.
Blown-in insulation depth and settling
Loose cellulose settles after it is blown in, so Greenfiber’s chart gives two depths for each R-value: how deep to blow it, and the depth it settles to and is rated at. For R-38 that is 11.2 inches blown and 10.4 settled. Owens Corning’s AttiCat chart lists the same number for its minimum thickness and its minimum settled thickness.
Check the depth in several places and blow to the deeper figure. Greenfiber’s chart says to put in both the bags per 1,000 square feet and the installed thickness it lists to reach the stated R-value, so count bags as well as inches.
Spray foam thickness
Spray foam is rated per inch, so its depth is the R-value divided by the rating: Huntsman rates its closed-cell Heatlok HFO High Lift at R-7.4 per inch and its open-cell Classic Ultra Select at R-3.7. The spray foam calculator turns an area and a target R-value into board feet, sets and kits.
Insulation thickness FAQ
How thick is R-38 insulation?
About 12½ inches as an Owens Corning PINK Next Gen batt, or 10¼ inches for its R-38C cathedral batt. Blown in, it is 13½ inches of AttiCat fiberglass or 10.4 inches of settled Greenfiber cellulose.
How thick is R-60 insulation?
No batt on Owens Corning’s sheet reaches R-60, so it is blown in or built from layers: 20½ inches of AttiCat fiberglass, or 17.3 inches of Greenfiber cellulose blown in to settle at 16.1.
How thick is R-49 insulation?
14 inches as a PINK Next Gen batt, 17 inches of AttiCat blown fiberglass, or 13.3 inches of settled Greenfiber cellulose.
How deep should attic insulation be?
Deep enough for your zone’s R-value. ENERGY STAR recommends R-49 for an uninsulated attic in zones 2 and 3 and R-60 in zones 4 through 8; in AttiCat blown fiberglass that is 17 or 20½ inches.
How thick is R-30 insulation?
10 inches as a PINK Next Gen batt (8¼ inches for the R-30C cathedral batt), 10¾ inches of AttiCat fiberglass, or 8.3 inches of settled cellulose.
Does blown-in insulation settle?
Cellulose does: Greenfiber’s chart has R-38 blown to 11.2 inches and rates it at the 10.4 inches it settles to. Owens Corning’s AttiCat chart gives the same depth before and after settling, 13½ inches at R-38.
Sources & method
Batt thicknesses are from Owens Corning’s PINK Next Gen data sheet (October 2024), blown fiberglass depths from its AttiCat coverage chart, cellulose depths from Greenfiber’s SANCTUARY coverage chart, and the zone levels from ENERGY STAR. Spray foam depths divide the R-value by the per inch ratings on Huntsman’s data sheets. Other brands publish their own charts with their own numbers.
- Owens Corning. PINK Next Gen Fiberglas Insulation Product Data Sheet (Pub. No. 10024913-A). October 2024
- Owens Corning. AttiCat PINK Blown-In Insulation, coverage chart. retrieved Nov 15, 2026
- US Greenfiber. SANCTUARY Attic Application Coverage Chart, 25 lb bag (DM-6.3-38 Rev F 05-26). Rev F 05-26
- ENERGY STAR (U.S. EPA). Recommended Home Insulation R-Values. retrieved Nov 15, 2026
- Huntsman Building Solutions. Classic Ultra Select Technical Data Sheet (AN 20.00178). REV 02.10.22
- Huntsman Building Solutions. Heatlok HFO High Lift Sell Sheet (AN 20.00060). REV 06.21.22
- Owens Corning. R-38C EcoTouch PINK Fiberglas Insulation for 2x12 Cathedral Ceilings, Product Data Sheet (Pub. No. 21151-D). June 2012
- Spray Foam Insulation Calculator: Board Feet, Kits & CostBoard feet of foam for an area at a thickness or a target R-value.
- Crawl Space Encapsulation: What the Code RequiresCrawl space wall R-values by climate zone under the 2021 IRC.
Marko Visic
I'm Marko Visic, a physics graduate who builds data-driven calculators. I run ConstructionCalc through my company, Moving Data Systems d.o.o.
The calculators help you plan a DIY job or check a contractor's quote before you sign. Each one cites its sources and shows its method, and cost figures are computed from public primary data. If a number looks wrong, email info@constructioncalc.org and I'll trace it to its source or fix it.