Stone wool insulation is manufactured by melting basalt and limestone at temperatures above 1450 °C and fiberising the melt through a spinner, yielding a non-combustible, water-repellent, vapour-permeable board or batt used across building envelope, industrial, and OEM sandwich-panel applications [S4][S5].
ROCKWOOL's published specification-guides library splits installation practice by assembly — interior mass walls, exterior rainscreen, interior partitions, and roofing — and the group's 03 Jun 2026 acquisition of ScanArc Plasma targets lower-carbon melting technology rather than product redesign [S1][S2][S3].
Material Properties That Govern Installation Decisions
Stone wool has a melting point above 1000 °C and is rated non-combustible under EN 13501-1 / ASTM E136 test regimes, which is why boards are specified as continuous exterior insulation behind combustible claddings and as fire stops in concealed spaces [S3][S6].
Water vapour passes through the open fibre matrix (μ ≈ 1) but bulk water is shed via a hydrophobic additive, so assemblies stay vapour-open on the warm side; the same behaviour lets a wet board be re-dried in service without permanent loss of R-value when dried back to design moisture content [S3].
Density selection is the lever installers actually control: Comfortboard 80 is the 80 kg/m³ rigid grade, Comfortboard 110 is the 110 kg/m³ rigid grade, and Cavityrock sits in the semi-rigid range for cavity/rainscreen walls [S6]. Higher density raises compressive strength for cladding screw-through loads, lowers acoustic resonance, and trims fibre shedding during handling.
Interior Partition Installation: Studs, Cavity Fill, and Acoustic Stagger
ROCKWOOL AFB is a lightweight batt sized for steel-stud interior walls and floors; AFB evo is the no-added-formaldehyde variant specified where indoor air-quality credits are tracked, and Safe'n'Sound® covers residential wood- and steel-stud partitions [S1].
Friction-fit the batt into the stud cavity, then add a separate row of resilient channel or staggered-stud framing on the finishing side; this decouples the gypsum from the structure and is what recovers the 8–12 dB wall assembly uplift that a single-layer partition with the same R-value batt cannot reach [S3].
Penetrations (outlet boxes, duct chases, plumbing) are sealed with intumescent acoustical sealant; a 6 mm continuous bead at the perimeter of the partition on both faces stops flanking sound, which is the dominant failure mode the Acoustic Transmission Class (STC) test never sees but the field always does [S3].
Exterior Continuous Insulation: Rainscreen, Cavity, and Screw Pattern
ROCKWOOL Cavityrock® is the semi-rigid stone wool board designed for exterior cavity and rainscreen applications, also available with a black mat facer for open-joint cladding; Comfortboard 80 and 110 are the rigid continuous-insulation (CI) grades used with screws-through-strapping or cladding-support systems [S1][S6].
Butt joints tight, stagger vertical seams at least one stud bay, and leave a minimum 10 mm vented air space between the board and the cladding back to keep the assembly rainscreen-vented; without that gap the board is functioning as a vapour-impermeable WRB bypass, not a drained rainscreen [S3][S6].
Fastener pattern follows the cladding weight: 1 fastener per 0.09 m² (≈ 305 mm grid) for typical fibre-cement, scaling to 1 per 0.04 m² (≈ 200 mm grid) for heavy tile or stone cladding; pull-through capacity is set by the lowest-density layer in the stack, which is the stone wool, not the cladding [S6].
Roofing and Industrial Board Installation: Membrane, Slope, and Compression
The Roofing Application Guide treats flat and low-slope decks as a layered system: deck → vapour control layer → stone wool (often two layers staggered) → mechanically fastened or adhered membrane; insulation compressive strength at 10 % deformation (≥ 60 kPa for service-trafficable assemblies) is the specifier's main check, not nominal R-value [S1].
Industrial boards are typically 40–120 mm thick stone wool with a density of 40–200 kg/m³ depending on service; the board is butted tight, mechanically pinned or adhered to the substrate, and seams taped or sealed where the operating temperature exceeds 200 °C and the assembly is a process-pipe or vessel cladding [S4].
Sandwich-panel factory lines use rock wool cores (40–80 kg/m³ density) between two metal skins for cleanroom and fire-rated partitions; the 2026 supplier catalogue lists 8,850 active Chinese suppliers of rock wool sandwich panels, with the rock wool core listed explicitly as the fire-stopping layer behind the metal skin [S7].
Selection Criteria: When Rock Wool Fits, When It Doesn't
Specify rock wool where the assembly needs a non-combustible core (Type I–IV construction, NFPA 285 wall, EN 13501-1 A1/A2-s1,d0), a vapour-open drying potential, or acoustic absorption at low frequencies (125–500 Hz), which the dense fibre matrix attenuates better than foam plastic of the same thickness [S3][S6].
Do not specify it where point-load compressive strength must exceed 200 kPa at 10 % deformation (cold-storage floor, heavy equipment base), where the cavity is below 25 mm (fibre orientation can't stabilise), or where the operating temperature is below the calculated dew point on the cold side and the cavity cannot be vented — moisture will accumulate inside the open matrix even though the board is hydrophobic [S3].
A density-vs-cost-vs-performance comparison for the four common grades:
— AFB (lightweight batt, ≈ 40 kg/m³): lowest cost, friction-fit interior partitions, lowest compressive strength, not for exterior CI. — Cavityrock (semi-rigid, ≈ 60–80 kg/m³): exterior cavity and rainscreen, balances drainage and handling. — Comfortboard 80 (rigid, 80 kg/m³): exterior CI behind claddings, balanced pull-through. — Comfortboard 110 (rigid, 110 kg/m³): high-compressive exterior CI, masonry support, screw-through-heavy-cladding assemblies [S6].
Common Failure Modes and Acceptance Criteria
Gaps and voids at the perimeter, compression of the batt in the cavity, and missing acoustical sealant at penetrations are the three field failures that erase installed performance; the diagnostic is a thermography scan in heating season (ΔT > 1 °C across the gap) or an acoustic leak at 50 dB pink noise during commissioning [S3].
Wet boards should be dried before enclosure: open the cladding or partition, run dehumidified air until the board returns to within 0.5 % by mass of dry weight, then re-close; do not enclose a board above 5 % moisture by mass — the trapped moisture will corrode metal cladding fasteners and produce a long-term vapour drive into the interior finish [S3].
Do not repair a stone wool board that has been compressed below 50 % of design thickness in service; replace the panel, because fibre orientation is permanently broken and the recovery is non-elastic under any reasonable load case.
For wider context on fire-rating class logic in built assemblies, the Fire Extinguisher Types and UL Ratings guide shares the same A/B/C/D fire-class language used in NFPA 285 wall assemblies. For substrate-prep sequencing on adjacent trades, the Fired Clay Brick Installation guide covers the heat-up and joint-control logic that masonry-clad rock wool assemblies inherit. For insulation-material taxonomy in equipment enclosures, the Nitrile Rubber NBR classifications article is a useful cross-reference on elastomer-grade selection.
For component-level specifications, see rock wool, linear guide, and crossed roller guide.