24 in. steel-stud module with 3 in. AFB absorption class
Key features
NRC 1.10 / SAA 1.08 at 3 in. per ROCKWOOL USA AFB TDS
Noncombustible stone wool; strong fire-reaction test narrative
Technical specifications
| Thickness | 3.0 in |
|---|---|
| Width | 24.0 in |
| Length | 48.0 in |
| Coverage | 80.0 sq ft/pack |
| Material | Stone wool (mineral wool), ROCKWOOL AFB® |
| Fire rating | Noncombustible per ASTM E136; 0/0 ASTM E84 per ROCKWOOL USA AFB TDS; cite listed partitions for hourly ratings. |
| Sound rating | NRC 1.10 and SAA 1.08 at 3 in. nominal thickness per ROCKWOOL USA AFB TDS (11-2025). |
| Density | Nominal density >2.5 lb/ft³ per ASTM C167 on ROCKWOOL USA AFB TDS. |
| Framing width | 24 in. batt width for 24 in. steel-stud layouts |
| Construction type | Interior steel-stud module (24 in. × 48 in. per ROCKWOOL USA AFB dimensional tables) |
| Application area | Interior partition walls and interior floor/ceiling cavities on 24 in. steel framing per ROCKWOOL AFB documentation. |
Product details
Open-plan offices, amenity corridors, and podium retail shells frequently use 24 in. steel studs for structural efficiency; insulation has to match the module or crews lose hours tweaking ears and shims. ROCKWOOL publishes 24 in. × 48 in. AFB batts so the wide bay gets continuous mineral fiber without ad-hoc piecing.
At 3 in. thick, the product inherits the manufacturer’s published NRC 1.10 and SAA 1.08 row from the 11-2025 USA data sheet. That is a meaningful step up from the 2 in. row for mid-frequency control when the partition designer is chasing NR curves or reducing flutter in large rooms.
Fire documentation parallels other AFB SKUs: noncombustibility, 0/0 ASTM E84 indices, and references to third-party rated assemblies in marketing collateral. Nothing changes about the need for listed details when the drawing specifies an hourly rating.
IDI lists supplier part 286368 at 80 square feet per package for the 3 × 24 × 48 configuration—align bids to that coverage and add realistic waste when walls have heavy door or glazing concentrations.
Always attach the dated PDF from https://p-cdn.rockwool.com/syssiteassets/o2-rockwool/documentation/technical-data-sheets/commercial/afb-acoustical-fire-batts-techdata.pdf to submittals so inspectors see the same tables you used in design.
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, ASTM C553 Type VII, CAN/ULC S702 Type I, ASTM E136 noncombustible, ASTM E84 flame spread 0 / smoke developed 0 (Class A per IBC Note 1 on TDS), UL GREENGUARD Gold and USDA BioPreferred 25% biobased per ROCKWOOL AFB product page
Frequently asked questions
When should I pick 3 in. AFB instead of 2 in.?
When should I pick 3 in. AFB instead of 2 in.?
Move to 3 in. when the acoustic model, partition STC target, or fire-cavity detail needs more thickness while still fitting the stud depth. Compare the NRC/SAA rows on the ROCKWOOL USA AFB TDS and coordinate with the tested wall assembly.
Is 80 sq ft per bag still accurate?
Is 80 sq ft per bag still accurate?
IDI’s listing for supplier part 286368 shows 80 square feet per package; confirm on the physical bag label whenever ROCKWOOL or the distributor revises bundle counts.
Can I compress the batt to fit services?
Can I compress the batt to fit services?
Chronic compression reduces effective thickness and can undermine both acoustic and fire-cavity intent. Relocate services, use approved relief details, or select a different thickness rather than permanently crushing the batt.
Where is Comfortbatt better?
Where is Comfortbatt better?
Comfortbatt is aimed at exterior thermal envelopes, attics, floors, and crawlspaces. AFB remains the interior acoustical fire batt line—do not swap them without revisiting hygrothermal and exposure details.