23 in. × 47 in. module for wood studs at 24 in. o.c. per USA TDS
Key features
R-15 at 3.5 in. labeled thickness in Comfortbatt thermal table
Flexible-edge stone wool; noncombustible with 0/0 ASTM E84 per TDS
Technical specifications
| R-Value | 15.0 |
|---|---|
| Thickness | 3.5 in |
| Width | 23.0 in |
| Length | 47.0 in |
| Coverage | 60.06 sq ft/pack |
| Material | Stone wool (basalt and recycled steel slag) |
| Fire rating | Noncombustible per ASTM E136; Flame Spread 0 / Smoke Developed 0 per ASTM E84 on ROCKWOOL USA Comfortbatt TDS (05-2025). |
| Sound rating | Wide-bay stone wool fill improves absorption versus empty 24 in. cavities; final acoustic metrics are assembly-dependent. |
| Density | >1.8 lb/ft³ per ASTM C167 on ROCKWOOL USA Comfortbatt TDS (05-2025). |
| Framing width | 24 in. on-center wood stud module (23 in. batt width per USA TDS) |
| Construction type | Wood stud framing |
| Application area | Exterior wood-framed walls at 24 in. o.c. plus attics, ceilings, exposed floors, and crawlspaces per ROCKWOOL when dimensions match. |
Product details
Twenty-four-inch stud spacing cuts lumber and labor when the structural design allows it, but insulation must match the bay or crews pay the difference in site cuts, compression, and thermal voids. ROCKWOOL publishes a 23 in. × 47 in. Comfortbatt module for wood studs at 24 in. on center; RXCB3523 is the R-15 / 3.5 in. thick SKU in that line.
The thermal table in the USA Comfortbatt data sheet (05-2025) ties labeled R-values to thickness for wood and steel families; verify your climate zone prescriptive requirement against the modeled assembly, especially if you pair cavity fill with continuous exterior insulation.
Stone wool’s reaction-to-fire statements on the sheet—ASTM E136 noncombustibility and ASTM E84 0/0 indices—are often why teams upgrade from combustible cavity options in wildland-urban interface or commercial-adjacent multifamily work.
Moisture and durability: Comfortbatt marketing emphasizes water repellency and low sorption in testing; the field still needs correct WRBs, tapes, and flashing to keep liquid water out of the wall.
Order using about 60.06 square feet per package as reflected in YEARS naming, then verify bundle counts at receipt.
Download https://www.rockwool.com/siteassets/o2-rockwool/documentation/technical-data-sheets/residential/comfortbatt-exterior-wood-and-steel-stud-thermal-batt-insulation-techdata-us.pdf for inspector-grade citations.
Documents & certifications
Technical data sheet
Manufacturer-tested R-value, coverage, fire notes, and handling—use for submittals, RFIs, and field QA.
Download PDF (opens in new tab)Certifications & compliance
ASTM C665 Type I compliant, ASTM E136 noncombustible, ASTM E84 flame spread 0 / smoke developed 0 (Note 1 Class A per IBC on TDS), ASTM C518 thermal resistance per published R-thickness table, GREENGUARD Gold per ROCKWOOL Comfortbatt marketing
Frequently asked questions
Will this fit 22-1/2 in. net stud spacing?
Will this fit 22-1/2 in. net stud spacing?
ROCKWOOL documents 23 in. width for 24 in. on-center wood framing. Verify actual plate layout and carpenter tolerances in the field before bidding to the last piece.
Is density identical on every Comfortbatt SKU?
Is density identical on every Comfortbatt SKU?
The USA TDS cites >1.8 lb/ft³ per ASTM C167 for the product family; plant-specific shipped density may vary within tested scope—confirm on submittals if required.
Can I double-layer for higher R-value?
Can I double-layer for higher R-value?
Layering must follow an approved assembly; avoid chronic compression that reduces effective thickness and R-value. Engineer the stack for structure, vapor, and fire continuity.
Does Comfortbatt need a kraft facing?
Does Comfortbatt need a kraft facing?
These batts are typically unfaced stone wool; vapor and air control belong to membranes and tapes selected for your climate zone and assembly drying strategy.