Rock wool boards are sold in density steps — 60, 80, 100, 120, 140 kg/m³ — and each step costs more per square metre than the one below it. Specifying the highest density is not “safer”; it is simply more expensive, and on some systems it is the wrong choice. Here is how the steps actually map to applications.
What density changes
- Compressive strength and rigidity — the higher the density, the more the board resists load, wind pressure and handling damage.
- Fire behaviour in a fire test — all our boards are A1 non-combustible, but denser boards hold their shape longer under fire exposure, which is what system fire tests look for in facades and roof build-ups.
- Acoustic mass — heavier boards give better airborne sound reduction in partitions and separating walls.
- Cost per m² — insulation is priced by weight at the factory gate, so the board cost rises roughly in proportion to density.
The density steps in practice
| Density | Typical use | Notes |
|---|---|---|
| 60 kg/m³ | Curtain-wall back-up, cavity insulation, light partitions | Lightest board for facades; use where wind load is modest and the board sits behind a rainscreen |
| 80 kg/m³ | Standard ETICS / exterior wall, general facade work | The workhorse density for most export markets |
| 100 kg/m³ | Exterior wall on mid- and high-rise, duct and equipment | Better resistance to wind pressure and site handling |
| 120 kg/m³ | High-rise facades, heavy facade systems, industrial | Chosen where the system’s fire test or fixing design calls for it |
| 140–150 kg/m³ | Roof boards, marine, high-load applications | Compressive strength is the driver, not thermal performance |
The two myths worth dropping
“Higher density means better thermal performance.” Not meaningfully. The thermal conductivity of rock wool sits in a narrow band — around ≤ 0.040 W/(m·K) for boards — across the normal density range. Thickness, not density, is what buys you R-value.
“Higher density is always safer for fire.” A1 non-combustible is a class, not a density. Once the product is A1 and the system is correctly detailed, the fire rating of the assembly comes from the design and the fixings as much as from the board.
How to check density on delivery
Weigh one pallet: net weight ÷ total volume (length × width × thickness × pieces). If the number lands within a couple of percent of the ordered density, the batch is what the test report says it is. This single check prevents the most common hidden cost in the rock wool trade — a “100 kg/m³” board that arrives at 82 kg/m³ and performs like an 80.
Choosing for your project
Work backwards from the requirement: the fire test and fixing design set the minimum density; the U-value requirement sets the thickness; the budget then decides whether you can buy that combination from a factory-direct source instead of a distributor. If you are unsure, send us the system and the target U-value and we will tell you the density and thickness we would ship.
Getting a price for your density
Taishi Rock Wool produces boards across 40–200 kg/m³ and 30–200 mm, 1200 × 600 mm standard, A1 non-combustible, GB/T 25975-2018. Browse exterior wall boards, roof boards or curtain wall boards — or send your specification for a factory quotation with a container loading plan. WhatsApp +86 175 6050 1246.
Related reading
- What Is Rock Wool Board? Manufacturing, Properties and Applications
- Rock Wool Thermal Conductivity and R-Value Explained
- Rock Wool vs Glass Wool Insulation Cost: What Actually Drives the Price
Related reading
- rock wool supplier for Indonesia
- rock wool supplier for Thailand
- what drives insulation price
- product range
Buyer questions we get most
Which density should I specify for a wall?
For external walls, 60–100 kg/m³ is the usual band; the higher end is specified where the board has to carry render, resist wind load or meet a fire-rated assembly.
Do I need a higher density for a sandwich-panel core?
Yes — cores are normally 100–120 kg/m³ because the insulation has to carry load. Our pipe sections and felt also run at 100 and 120 kg/m³, so the higher band is standard production rather than a special order.
Does density change the insulation value?
Not much. Insulation value comes from thickness and thermal conductivity, so choose density for strength, fire and acoustics — then set thickness for the R-value you need.
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