When choosing insulation materials for building envelopes and technical insulation, planners and experts are often faced with a key decision: glass wool or rock wool? Both materials belong to the mineral wool family and offer excellent properties in terms of fire protection and sound insulation. But from a technical point of view, there are decisive differences. This article highlights the advantages of glass wool - particularly with regard to Volume weight and Lambda value - taking into account current standard requirements and building practice in Switzerland.
Volume weight: Lightness as a physical advantage
The density (bulk density) influences key aspects such as statics, processing and transport. Glass wool scores points here with its usually significantly lower weight. Typical values for glass wool are in the range of 10 to 50 kg/m³, while stone wool is often classified as 40 to 150 kg/m³ - depending on the product and area of application.
The lower material requirement per cubic metre not only reduces the weight of the construction, but also facilitates handling and installation - a significant advantage when used in pitched roofs, timber frame construction or in the renovation of old buildings. The low density also pays off ecologically in everyday life on construction sites in Switzerland - thanks to less material used per cubic metre, lower transport emissions and a smaller carbon footprint.
Lambda value: Better thermal conductivity for energy-efficient construction
The lambda value (λ) describes the thermal conductivity of an insulating material and is a decisive criterion for the thermal quality of the building envelope - the lower the value, the better the insulating effect. Glass wool generally achieves better lambda values than rock wool.
- Glass woolλ = 0.030-0.038 W/(m-K)
- Rock wool: λ = 0.033-0.045 W/(m-K)
This difference enables a lower insulation thickness with the same U-value or improved insulation performance with the same construction thickness. In climatic regions such as Switzerland, with cold winters and increasingly hot summer periods, this not only supports compliance with SIA standards (e.g. SIA 380/1), but also optimises thermal insulation in summer and energy efficiency.
Further technical advantages of glass wool
In addition to its density and lambda value, glass wool offers additional technical advantages:
- Compression behaviour: Glass wool is more elastic and adapts more easily to unevenness during installation, an advantage in the airtight construction of structures.
- Recycled content and sustainability: Glass wool often contains over 50 % recycled glass - a plus for the environmental balance.
- Fire protection: Like rock wool, glass wool is also in fire behaviour class A1 and meets the highest requirements for structural fire protection.
Conclusion: Glass wool as a sustainable insulation material
Glass wool is a convincing choice for many applications - especially in residential construction, timber construction and energy-efficient renovations. The lower weight simplifies logistics and installation, while the better lambda value increases the insulation performance. So if you are looking for an economical, sustainable and high-performance solution, modern Glass wool well advised.