Rock wool is one of the most widely used insulation materials in Europe. It provides thermal insulation, sound insulation and fire protection at the same time, something no other common insulation material can do.
In the Greek market it is mainly used in external wall insulation (ETICS) and interior wall insulation, but many people do not know exactly what it is, what its real properties are and when it is worth choosing it over polystyrene.
Rock wool (mineral wool, stone wool) is an inorganic fibrous insulation material produced from natural rock, mainly basalt and slag. The rock is melted in a furnace at temperatures of 1,300°C to 1,600°C and the molten material is spun under high pressure, creating fine fibres 4–5 μm in diameter. The fibres are bonded with special thermosetting resins and the final product is cut into boards or rolls.
The result is a material with extremely low thermal conductivity, high non-combustibility and excellent sound-absorbing properties that come from its fibre structure.
To be sold legally on the Greek market, rock wool must be certified to European Standard EN 13162 in accordance with EU Regulation 305/2011.
These are the key technical characteristics that determine the performance of rock wool:
No. Rock wool is a completely non-combustible material, Class A1 to European Standard EN 13501-1. Its fibres withstand temperatures above 750°C, far higher than those reached in a typical house fire.
This means that it does not ignite, does not give off toxic gases when exposed to fire and acts as a barrier that slows the spread of fire, giving valuable time for safe evacuation.
It is precisely this property that makes rock wool the only acceptable choice for thermal insulation in multi-storey buildings, schools, hotels and commercial buildings with increased fire safety requirements.
Not for the end user. In the past its fibrous composition was linked to possible health risks, but research never proved this. The European Chemicals Agency classifies rock wool insulation as non-carcinogenic and non-toxic.
The only precaution needed concerns installers during fitting: fibres released during cutting can irritate the skin and lungs. That is why installation must be carried out by a specialist crew with suitable personal protective equipment.
Rock wool and polystyrene (styrofoam) have similar thermal insulation performance, but they differ significantly in three critical areas: fire protection, sound insulation and breathability.
Related Article: For more on roof insulation materials, read the complete roof insulation guide.
Three main fibrous insulation materials are on the market and they often cause confusion:
| Characteristic | Rock wool | Mineral wool | Glass wool |
|---|---|---|---|
| Raw material | Basalt | Improved glass wool | Glass |
| Colour | Dark green | Brown-green | Yellow |
| Density | High | Medium | Low |
| Non-combustibility | A1 (excellent) | A1 | A1 |
| Ideal for | External wall insulation, heavy-duty applications | Interior insulation, drywall construction | Plasterboard, budget solution |
| Cost | Higher | Medium | Lower |
The ideal application when external insulation is not possible
At Goumas Insulation we use aluminium-faced Knauf Insulation Chimenea mineral wool, 30 mm, with a density of 50 kg/m³ and Knauf H2 plasterboard. All work is carried out indoors, regardless of the weather.
Technical data:
Advantages:
Read more about interior wall insulation
Rock wool as an alternative to polystyrene for special requirements
For typical homes in Attica we recommend Neopor (graphite-enhanced expanded polystyrene). Rock wool is chosen where there are increased fire safety requirements or legal obligations.
Suitable for:
Advantages:
Read more about external wall insulation (ETICS)
Noise reduction of up to 50% with thermal insulation at the same time
It is fitted inside the metal plasterboard frame. It absorbs both airborne noise (voices, television) and impact noise (footsteps, furniture). For enhanced sound insulation, a second layer of plasterboard or a viscoelastic membrane is added.
Suitable for:
Advantages:
Complete guide to foam concrete and roof falls
In some roof applications, aluminium-faced mineral wool is used beneath the slab as a vapour barrier. This is combined with foam concrete for the falls and XPS insulation boards, creating a complete system. For more on roof falls and foam concrete, read our complete guide.
See interior wall insulation with mineral wool
If you are considering interior wall insulation or external wall insulation (ETICS) and are not sure which material suits your situation, an on-site assessment is the right first step. Every building has different needs, and the choice of material can only be made after an inspection.
With 25+ years of experience in building insulation, certified crews and a written guarantee for every project, Goumas Insulation will help you choose the right solution for your building's needs.
Essentially they are variations of the same type of fibrous material with different raw materials and binders. Rock wool is made from basalt and has higher density and mechanical strength. Mineral wool (e.g. Knauf ECOSE) is lighter, uses more environmentally friendly binders and is better suited to interior drywall applications.
For typical homes, Neopor expanded polystyrene is the most widespread and economical choice. Rock wool is chosen where there are increased fire safety requirements, such as in multi-storey buildings, buildings close to forests or buildings with legal fire safety obligations.
The basic system with a metal frame, 5 cm mineral wool and Knauf plasterboard starts from €65/m² (plus VAT). For an enhanced system with a sound insulation membrane or fire-resistant plasterboard, from €85/m². See our price list for detailed prices.
No. Because interior insulation is not exposed to outdoor weather conditions, it requires no maintenance. The material's service life is practically unlimited under normal conditions of use.
Not usually. XPS boards are used for roof insulation because of their zero water absorption and high mechanical strength. Rock wool absorbs water if exposed to moisture without suitable protection. See our roof thermal insulation solutions.
For interior wall insulation, usually 5 cm. For external wall insulation, typically 8–10 cm depending on KENAK requirements and the climate zone.
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