R-23 at 5.5 in. for 16 in. o.c. wood studs (15.25 in. × 47 in.)
Key features
Designed for nominal 2×6 stud depths—not 2×4 cavities at full thickness
Flexible-edge stone wool; noncombustible with 0/0 ASTM E84 per TDS
Technical specifications
| R-Value | 23.0 |
|---|---|
| Thickness | 5.5 in |
| Width | 15.25 in |
| Length | 47.0 in |
| Coverage | 39.82 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 | Thick cavity stone wool improves facade noise control versus minimum fills; STC results require full partition design. |
| 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 (nominal 2×6), attics, ceilings, and exposed floors per ROCKWOOL when 5.5 in. R-23 batts fit the cavity. |
Product details
Energy codes elevated typical exterior wall targets into the 2×6 prescriptive world in many jurisdictions. RXCB551525 targets that reality with R-23 at 5.5 in. labeled thickness in the 15.25 in. × 47 in. wood module—full contact in the bay matters because an under-filled 2×6 leaves performance on the table.
Stone wool’s noncombustible reaction to fire and moisture story—ASTM E136 and ASTM E84 0/0 on the Comfortbatt USA sheet—is a common specifier motivation when durability and wildfire-adjacent narratives join energy compliance.
Pair cavity R-23 with continuous exterior insulation when your modeled assembly needs it; the batt handles stud-bay conduction while CI attacks bridging through framing members.
Installation pitfalls include chronic compression behind utilities, poorly detailed box extenders, and air leakage at the sheathing plane—insulation cannot compensate for a disconnected air barrier.
Use about 39.82 square feet per package for estimating from YEARS data; verify label counts at delivery.
Attach https://www.rockwool.com/siteassets/o2-rockwool/documentation/technical-data-sheets/residential/comfortbatt-exterior-wood-and-steel-stud-thermal-batt-insulation-techdata-us.pdf (05-2025 issuance) to submittals and update when superseded.
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
Is this for 2×4 or 2×6 walls?
Is this for 2×4 or 2×6 walls?
The 5.5 in. thickness and R-23 label correspond to nominal 2×6 stud depths at 16 in. o.c. per ROCKWOOL’s wood-stud thermal table. Do not install full-thickness 5.5 in. batts into 3.5 in. 2×4 cavities.
How much wall area per bag?
How much wall area per bag?
Expect roughly 39.82 square feet per package under published SKU data; confirm on the pallet or master-pack label.
Does Comfortbatt alone fix party-wall STC?
Does Comfortbatt alone fix party-wall STC?
Stone wool helps, but STC is assembly-dependent: gypsum layers, resilient channels, and perimeter seals often dominate results.
Who sets cladding fastener schedules?
Who sets cladding fastener schedules?
Fastener length and density follow engineering for cladding weight, wind load, and furring—do not infer structural attachment from the insulation SKU.