Most complaints about stone wool cores start on the panel line, not in the building. The strip arrives, the line runs, and the panel comes out with soft edges, uneven density at the joint, or delamination after foaming. In almost every case the cause is the same: the purchase order specified “stone wool strip 100 kg/m³, 150 mm” and left everything else to the supplier. This guide lists the numbers worth fixing in writing.
What the strip actually does in a panel
A mineral-wool sandwich panel is a composite: two steel skins, a rigid foam that bonds them, and stone wool strips laid perpendicular to the skins to carry the fire and acoustic performance. The strips are not insulation filler — they are the structural and fire-resisting element. That is why the specification has to be treated like a structural component, not like loose insulation.
The six numbers to fix in the purchase order
- Density (kg/m³) — 80 to 120 kg/m³ covers the great majority of cold-room, warehouse and factory panel lines. Density drives compressive strength and how the strip behaves when the foaming pressure pushes against it. Below 80 kg/m³ the strip tends to compress unevenly and the panel loses flatness.
- Strip width and tolerance (mm) — normally cut to the panel’s core thickness, with a tolerance in the order of ±1 mm. Loose tolerance shows up as gaps that the foam has to bridge, which is where delamination begins.
- Squareness and flatness — the strip must sit perpendicular to the skins. A strip that is out of square by a couple of millimetres per metre creates visible telegraphing on the finished panel face.
- Fibre orientation — vertical fibre (fibre running through the thickness) gives the compressive strength and fire behaviour that panel cores are specified for. Confirm the orientation, don’t assume it.
- Facing — plain, or with a foil / glass-tissue facing to improve adhesion to the foam system. If your foaming line uses a specific PU system, check compatibility with the strip’s surface before you commit to containers.
- Length and packing — cut lengths matched to the line reduce waste and labour. Ask for the loading plan: how many pieces per pallet and how many m³ fit a 40HQ at your strip thickness.
Typical specification
| Property | Typical value |
|---|---|
| Density | 80–120 kg/m³ (up to 150 on request) |
| Strip width | Cut to your panel core thickness, e.g. 100–200 mm |
| Strip length | 1200 mm standard, cut to line length on request |
| Thermal conductivity | ≤ 0.045 W/(m·K) |
| Fire rating | A1 non-combustible |
| Standard | GB/T 25975-2018; EN 13162 and ASTM C612 reports on request |
How to de-risk the first order
- Ask for a batch test report, not a catalogue sheet. Density is the number that gets quietly reduced between the sample and the third container.
- Run a line trial. A pallet of strips through your own line, with your own foam and your own curing conditions, tells you more than any certificate.
- Weigh one pallet on arrival. Net weight divided by volume gives you the real density. It takes two minutes and settles any discussion about the delivery.
- Keep the spec in the PO. Density, width tolerance, squareness, fibre orientation, facing and packing — if it is not in writing, it is not a requirement.
Sourcing the strip
Taishi Rock Wool produces stone wool strips at 80–120 kg/m³, cut to your line’s dimensions, from a factory with 800,000 tonnes of annual capacity and ten production lines. See the stone wool strip range, or send us your line specification — strip width, core thickness, foam system and monthly volume — and we will reply with a factory price and a loading plan. WhatsApp +86 175 6050 1246.
Related reading
- Rock Wool for Cold Storage and Sandwich Panels: Fire-Safe Insulation Guide
- How to Import Rock Wool from China: A Complete 7-Step Guide
- Rock Wool vs Glass Wool Insulation Cost: What Actually Drives the Price
Sourcing by market
Buyer questions we get most
Why use strips instead of boards in a panel core?
Strips are cut with the fibre oriented across the thickness, so the core resists compression instead of delaminating. Boards are used where the insulation is fixed to a surface rather than laminated into a panel.
What should be written into the panel specification?
Density, strip width and thickness with tolerances, fibre orientation, the facing or adhesive, fire class, and the dimensional standard the panel must meet.
Can strips be supplied cut to our panel line?
Yes — cut-to-size strips are produced to the panel maker’s dimensions so the lamination line does not have to trim.
About this guide
Who maintains it
This guide is maintained by the Taishi Rock Wool export team in Shandong, China — factory-direct rock wool and glass wool from seven production bases with a combined capacity of 800,000 tonnes a year. Technical questions go straight to the factory rather than to a trading desk: WhatsApp +86 175 6050 1246 or email cliu32626@gmail.com.
Standards and sources referenced
- GB/T 25975-2018 — Chinese national standard for rock wool and its products; our production and test reports follow it.
- EN 13162 — European product standard for mineral wool, including how thermal conductivity (λ) is declared.
- EN 13501-1 — fire classification of construction products; class A1 means non-combustible.
- ISO 8301 / ASTM C518 — steady-state thermal conductivity test methods behind any quoted λ figure.
- ASHRAE Handbook—Fundamentals — definitions of thermal conductivity and R-value used here.
- EURIMA — European Mineral Wool Manufacturers Association, technical guidance on mineral wool performance.
- Insulation Institute (NAIMA) — industry technical resources on insulation performance and specification.
Last updated: September 23, 2026