R-15 at 3.5 in. for 16 in. o.c. wood framing (15.25 in. × 47 in. per USA TDS)
Key features
Flexible long edges engineered for stud contact and stable cavity R-value
Noncombustible stone wool with 0/0 ASTM E84 indices in manufacturer TDS
Technical specifications
| R-Value | 15.0 |
|---|---|
| Thickness | 3.5 in |
| Width | 15.25 in |
| Length | 47.0 in |
| Coverage | 59.73 sq ft/pack |
| Material | Stone wool (basalt and recycled steel slag) |
| Fire rating | Noncombustible per ASTM E136; Flame Spread Index 0 and Smoke Developed Index 0 per ASTM E84 (UL 723) on ROCKWOOL USA Comfortbatt TDS (05-2025); Note 1 Class A per IBC. |
| Sound rating | Stone wool fiber matrix improves sound absorption versus an empty stud cavity; published STC requires tested wall assemblies—Comfortbatt supports the partition but does not replace assembly documentation. |
| Density | >1.8 lb/ft³ per ASTM C167 on ROCKWOOL USA Comfortbatt TDS (05-2025). |
| Framing width | 16" OC |
| Construction type | Wood stud framing |
| Application area | Exterior wood-framed walls, attics, ceilings, exposed floors, and crawlspaces per ROCKWOOL Comfortbatt applications when15.25 in. × 47 in. R-15 batts match the design. |
Product details
Wood-frame crews lose energy when batts bridge poorly at corners, shrink from studs, or leave chronic shadows at the face layer. Comfortbatt’s flexible-edge detail is meant to compress on insertion and recover against framing so the labeled thickness—and the R-value tied to that thickness in ASTM C518 testing—survives inspection better than loosely gapped fills.
RXCB351525 is the R-15 / 3.5 in. thick format in ROCKWOOL’s published wood-stud table for 16 in. on-center layout (15.25 in. width × 47 in. length per the USA technical data sheet dated 05-2025). That module tracks the common net bay width for 2× studs at 16 in. o.c. while keeping eight-foot wall math predictable for courses and cuts.
Fire and reaction-to-fire language on the same sheet positions Comfortbatt as noncombustible to ASTM E136 with Flame Spread Index 0 and Smoke Developed Index 0 to ASTM E84 (Note 1 references Class A expectations per IBC in the footer). Those are material-level statements; rated assemblies still require listed details when the drawing specifies an hourly partition or penetration.
Moisture narratives in manufacturer literature emphasize low water-vapor sorption and published vapor transmission data for representative thicknesses—pair that with your climate zone’s WRB, flashing, and air-barrier strategy rather than assuming the batt alone manages liquid water.
Acoustically, stone wool’s fiber structure damps noise compared with empty cavities; whole-wall STC remains assembly-dependent (mass, spacing, seals).
Estimate orders using about 59.73 square feet per package as carried in the YEARS SKU naming, then reconcile to the master-pack label and realistic waste at openings, ducts, and engineered beams.
Download the current Comfortbatt USA PDF at https://www.rockwool.com/siteassets/o2-rockwool/documentation/technical-data-sheets/residential/comfortbatt-exterior-wood-and-steel-stud-thermal-batt-insulation-techdata-us.pdf and product overview at https://www.rockwool.com/north-america/products-and-applications/products/comfortbatt before code submittals.
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
What framing module is RXCB351525 cut for?
What framing module is RXCB351525 cut for?
ROCKWOOL’s USA Comfortbatt data sheet lists wood studs at 16 in. on center as 15.25 in. wide by 47 in. long for this product family; RXCB351525 is the R-15 / 3.5 in. thick SKU in that module.
Is Comfortbatt the same as Comfortboard 80?
Is Comfortbatt the same as Comfortboard 80?
No. Comfortbatt is a semi-rigid cavity batt for stud bays. Comfortboard 80 is a higher-density rigid continuous insulation board for outboard CI strategies—different products and attachment details.
Does labeled R-15 equal whole-wall performance?
Does labeled R-15 equal whole-wall performance?
The R-value on the bag references the insulation product tested per ASTM C518. Whole-wall R-value still depends on framing factor, thermal bridging, continuous insulation, and air leakage—model the assembly for code compliance.
Can I install this in interior partitions only?
Can I install this in interior partitions only?
Comfortbatt is marketed for exterior wood- and steel-frame applications plus attics, ceilings, floors, and crawlspaces per ROCKWOOL literature. Interior use may be acceptable when dimensions and code paths match—confirm with your specifier.