Rockwool Insulation — Blanket, Board, Slab & Pipe Sections

What Are Rockwool Insulation Slabs?

Rockwool insulation slabs — also known as stone wool boards or mineral wool panels — are rigid, high-density thermal insulation products manufactured from natural basalt rock and recycled slag. The raw materials are melted at over 1,450°C and spun into fine fibers, then compressed into boards of precise density and thickness.

Unlike flexible blankets or loose-fill insulation, rockwool slabs offer structural rigidity while maintaining exceptional thermal, acoustic, and fire-resistant properties. This makes them the preferred choice for:

• External wall insulation systems (ETICS/EIFS)
• Sandwich panel cores for cold storage and clean rooms
• Flat roof insulation with high compressive strength
• Partition walls requiring fire-rated separation
• Industrial equipment and high-temperature piping

Our slabs are available in densities from 40 to 200 kg/m³ and thicknesses from 25mm to 200mm, ensuring a perfect match for every application — from lightweight residential cavity walls to heavy-duty industrial furnace linings.

Rock Wool, Rockwool, Stone Wool or Mineral Wool — What Is the Difference?

If you have searched for rockwool insulation, rock wool, stone wool and mineral wool and wondered whether they are four different products, they are not. All four names describe the same family of man-made vitreous silicate fibres spun from molten rock.

• Rockwool / rock wool — the spelling buyers use most. One word or two, it means the same stone wool insulation made predominantly from basalt.
• Stone wool — the formal European term. EN 13162, the product standard for factory-made mineral wool, uses "stone wool" for rock-based fibre.
• Mineral wool — the umbrella term used in ASTM specifications. It covers both stone wool made from basalt and slag wool made from blast-furnace slag. When a data sheet says mineral wool, check which base rock it is.
• Basalt wool — a descriptive name pointing at the raw material. Our rockwool is basalt-based, with dolomite added as a flux and a controlled share of recycled slag.

In practical terms: if your specification calls for mineral wool board at 650 °C, a basalt stone wool board is the right substitution. If it calls for rock wool blanket, you want the flexible needled mat rather than the rigid board. The rest of this page uses all four names interchangeably, because that is how the market searches for them.

Rockwool Temperature Rating: Service Limit, Softening Point and Melting Point

Short answer: the rockwool max temperature for continuous service is 650 °C, and the melting point is above 1000 °C. Every rockwool temperature rating printed on a data sheet traces back to one of those two numbers.

Temperature is the most mis-specified property of rockwool. Four different numbers circulate, and mixing them up is how insulation ends up over-heated in service.

Why you will sometimes see 750 °C quoted. That figure is the furnace temperature in the ASTM E136 vertical-tube test — the procedure used to prove a material is non-combustible. It is a test condition, not a service rating. Sizing rockwool for 750 °C continuous duty is the most common specification error we see; for anything sustained above 650 °C, specify ceramic fiber blanket (1100–1430 °C classification) or calcium silicate insulation instead.

Thermal conductivity rises with temperature, so the 0.036 W/(m·K) printed on a room-temperature data sheet is not the value at 400 °C:

That is why a rockwool temperature rating has to be read together with the temperature at which conductivity was measured — never on its own.

Is Rockwool Combustible? Mineral Wool Fire Rating Explained

No. Rockwool — like every stone wool and mineral wool product in our range — is non-combustible and not flammable. It carries an A1 classification to EN 13501-1, the highest reaction-to-fire class available in Europe, and it passes ASTM E136 without igniting.

The reason is chemistry: the raw material is already an oxidised rock. Basalt that has been melted at 1500 °C and re-solidified has nothing left to burn. In a fire, rockwool does not ignite, does not spread flame, does not release flaming droplets, and generates no significant smoke. Its melting point above 1000 °C means the fibre mat stays in place as a barrier long after organic insulations have gone.

What that delivers in practice:

• Fire resistance of assemblies — partitions, shafts and floors built with stone wool routinely achieve 60, 90, 120 and up to 240 minute ratings when tested to EN 1364 / EN 1365 or ASTM E119 as a complete system. The rating belongs to the assembly, so always specify the tested build-up, not just the board.
• Fire stopping and penetration seals — high-density rockwool slab is the standard backing material behind sealants and collars.
• Structural fire protection — rockwool board and wired mat protect steel beams, columns and ductwork.
• Fireplace and furnace surrounds — mineral wool insulation is safe around fireplaces and appliance housings, provided the sustained temperature at the insulation face stays within 650 °C. Where flue gas or radiant heat pushes past that, switch the hot face to ceramic fiber.

If your project documents ask for "fire rated mineral wool", what is normally required is: an A1 classification, a declared melting point above 1000 °C, a density appropriate to the tested assembly (usually 80–150 kg/m³ for fire boards), and a certificate for the specific build-up.

Rockwool Product Forms: Blanket, Board, Slab and Pipe Section

Rockwool Blanket

Rockwool blanket — also sold as rock wool roll, felt or wired mat — is a flexible, needled mat of stone wool fibres. It is the form to choose when the surface is curved, irregular or too large to board out: tanks, boilers, large-diameter ducts, kiln backs and roof decks.

• Densities 40–120 kg/m³, most commonly 60, 80 and 100 kg/m³
• Thickness 25–200 mm, single or multi-layer
• Supplied plain, with wire mesh reinforcement (wired insulation blanket), or stitched to galvanised hex mesh for vertical and overhead runs
• Also supplied with a glass mesh facing where a plaster or render finish follows

See rock wool blanket, wired insulation blanket and glass-mesh faced blanket.

Rockwool Board and Slab

A rockwool board — the same product called a rock wool slab across much of Asia and the Middle East — is a rigid, dimensionally stable panel. It carries compressive load, accepts fixings and renders, and is the form used in building envelopes.

• Densities 40–200 kg/m³; 80–150 kg/m³ covers most wall, roof and fire applications
• Standard size 1200 × 600 mm; 1000 × 600 mm and cut-to-size on request
• Thickness 25–200 mm, including the widely specified 100 mm board at 1200 × 600 mm
• Edge profiles: square, tongue-and-groove and shiplap

See rock wool board and rock wool strips for cavity and perimeter detailing.

Rockwool Pipe Section

Rockwool pipe insulation is supplied as a moulded pipe section — a pre-formed, split cylindrical shell that clamps around the pipe and is strapped or wired in place. Moulded sections install faster and insulate more evenly than wrapped blanket, and they hold their circular geometry under cladding.

• For pipe outer diameters from 15 mm to over 600 mm
• Wall thickness 25–100 mm, sized to the required heat loss or condensation control
• Densities 80–150 kg/m³
• Plain, or factory-faced with aluminium foil, kraft paper or glass cloth

See rock wool pipe insulation for the size range and data sheet.

Rockwool Technical Data Sheet

Typical values for standard grades. Project-specific certificates are issued with every shipment.

Governing product standards: EN 13162 for factory-made mineral wool used in buildings, ASTM C612 for mineral fiber block and board, ASTM C553 for mineral fiber blanket, and ASTM C547 for mineral fiber pipe insulation. Every shipment is produced under an ISO 9001 quality system with batch traceability.

Rockwool vs Glass Wool, Ceramic Fiber and Aerogel

Rockwool vs glass wool. The most asked comparison, and the answer turns on temperature and load. Glass wool has slightly lower conductivity at room temperature and costs less per square metre, but it is limited to roughly 400 °C and it will not carry load. Rockwool is the choice above 400 °C, wherever compressive strength or dimensional stability matters, and wherever a fire resistance rating is being claimed. For an ambient-temperature building cavity with no fire requirement, glass wool is often the more economical buy; for anything hot, loaded or fire-rated, rockwool wins. Compare glass wool insulation.

Rockwool vs ceramic fiber. This is a temperature line, not a quality comparison. Below 650 °C, rockwool is cheaper, stronger and easier to handle; above it, rockwool cannot survive and ceramic fiber blanket (1100–1430 °C classification) is the correct material. Furnace hot faces, kiln car tops and burner blocks belong to ceramic fiber, while the back-up layer behind them is frequently rockwool. See ceramic fiber insulation.

Rockwool vs aerogel. An aerogel blanket delivers roughly two to three times the thermal resistance per millimetre, which is what justifies its price where space is the binding constraint: congested pipe racks, valve clusters, offshore modules. Where thickness is not constrained, rockwool reaches the same heat-loss target for a fraction of the cost, which is why many projects use aerogel only at the tight spots and rockwool everywhere else. See aerogel insulation.

Where Rockwool Insulation Is Used

• Industrial pipe insulation — hot process lines, steam mains, condensate return and chemical plant piping up to 650 °C, typically as moulded pipe sections under aluminium or stainless cladding. See rock wool pipe insulation.
• Marine and offshore — A1 non-combustible, low smoke and vibration resistant, which is why rockwool marine insulation is specified for engine room bulkheads, accommodation fire divisions, HVAC ducts and pipe runs on ships and platforms. Deck and bulkhead ratings are typically achieved with 60–120 kg/m³ boards inside tested assemblies.
• Tanks, vessels and boilers — blanket or wired mat over large curved surfaces, banded and clad.
• Furnace and oven back-up — as the secondary layer behind a ceramic fiber hot face, and around appliance and fireplace housings where the sustained face temperature stays under 650 °C.
• External wall insulation — boards in external thermal insulation composite systems, rainscreen cladding and curtain wall spandrels. Being vapour open, it does not trap interstitial condensation.
• Roofs and floors — high-density boards under membranes and under screed, where compressive strength governs.
• Acoustic treatment — partition walls, machine enclosures, generator rooms and studios. For dedicated acoustic finishes see rock wool acoustic panels.
• Power generation and petrochemical — turbine halls, flue gas ducts, reformer and cracker piping.

Browse the full application library for detailed build-ups.

How Rockwool Is Made

1. Raw material selection — basalt is blended with dolomite, which acts as a flux and lowers the melt temperature, plus a controlled share of recycled blast-furnace slag. The blend is set to hold the acidity coefficient at or above 1.6, the ratio that governs long-term durability and moisture resistance.
2. Melting — the charge is melted in a cupola or electric furnace at around 1500 °C.
3. Fibre forming — the melt stream falls onto high-speed centrifugal spinning wheels, which throw it into fibres 4–7 µm in diameter. Wheel speed and melt viscosity set the fibre fineness, and finer fibre means lower conductivity at a given density.
4. Binder application — a thermosetting resin and a water-repellent oil are sprayed onto the fibre wool while it is still hot.
5. Collection and curing — fibres gather on a moving conveyor as a primary fleece, then pass through a curing oven that polymerises the binder and locks in thickness and density.
6. Finishing — the cured mat is cut, slit and rolled as blanket, or trimmed to size as board, faced where required, and packed.

Because density and thickness are set at the forming and curing stages rather than by tooling, custom densities and non-standard thicknesses are produced to order without a tooling charge.

Rockwool Acoustic Insulation: Sound Absorption and Noise Control

Rockwool's open, non-directional fibre structure makes it one of the most effective acoustic insulators available — it absorbs sound energy across a broad frequency range rather than merely blocking it. That is why it is specified for both building acoustics and heavy industrial noise control.

• Noise Reduction Coefficient (NRC): typically 0.70–0.95 depending on density and thickness — denser, thicker slabs absorb more low-frequency energy.
• Where it is used: party walls and floor-ceiling build-ups, HVAC plant rooms, studio and cinema linings, generator and compressor enclosures, ship engine rooms, and external acoustic barriers.
• How it works: the fibrous mat converts incident sound into tiny amounts of heat through viscous friction in the pores. A sealed air gap or mass-loaded layer boosts low-end performance further.
• Fire plus acoustics in one layer: because rockwool is A1 non-combustible, it delivers sound control and fire resistance in the same build-up — a combination mineral-foam acoustic products cannot match.

For dedicated acoustic products see our rock wool acoustic panels. For full application build-ups across marine, power, petrochemical and building sectors, browse the applications library.

How to Specify Rockwool: A Buyer's Checklist

Give your supplier these six numbers and the quote comes back right the first time:

1. Operating temperature — continuous and peak. Above 650 °C you need ceramic fiber or calcium silicate.
2. Form — blanket, board or slab, or moulded pipe section; for pipe, add the outer diameter and the required insulation thickness.
3. Density — 60–80 kg/m³ for general thermal and acoustic duty; 100–150 kg/m³ where the board carries load or a fire rating; 150–200 kg/m³ for high-compression roof and deck work.
4. Dimensions — thickness, plus board size if non-standard. 1200 × 600 mm is stock.
5. Facing or reinforcement — none, wire mesh, glass mesh, aluminium foil or kraft paper.
6. Compliance documents — EN 13501-1 A1 certificate, EN 13162 or ASTM declaration, ISO 9001 traceability, and any project-specific third-party inspection.

Two specification traps are worth avoiding: quoting a room-temperature conductivity for a high-temperature duty, and asking for a fire rating on the material alone rather than on the tested assembly.