Technical Manager, Helen Moss, explains how stone wool insulation can help the building designer satisfy thermal, fire, and acoustic requirements for façade constructions.

Cladding constructions are an increasingly common method of construction. When compared to more traditional methods, such as masonry cavity walls, cladding constructions can be lightweight and quick to construct making them an ideal choice for large and high rise buildings. As with all areas of the construction market, Building Regulations play a defining part in the way products are specified. In particular, recent and ongoing changes to the fire regulations restrict the use of certain materials, whilst requiring the use of others – such as non-combustible materials.

A typical façade construction may attach to a main load bearing structure of concrete or metal framing with a lighter weight metal infill. Over the outside of this frame may sit sheathing boards, insulation and the final covering, or façade, to the building. This façade can be one of a variety of finishes from traditional masonry cladding to ventilated rainscreen cladding.

The main insulation zone in a façade construction should be over the outside of the supporting framework behind the cladding, separated from this by a ventilated cavity. The choice of insulation in this location is key to the overall performance of the building, whether that is improving the thermal performance of the building envelope or enhancing the acoustic comfort for those living or working in the building. Some products will also have aesthetic implications for a building designer.

External walls form the largest surface area of the building’s thermal envelope and the correct specification of insulation can help towards meeting the energy performance requirements of the building. With a typical thermal performance of around 0.035 W/m.K and availability in a wide range of thicknesses, stone wool products can be considered by designers to assist in achieving these energy requirements. Some manufacturers offer additional assistance to the designer with the provision of thermal calculations to help ensure that the desired performance is met.

The upcoming changes to Part L mean that greater focus is likely to be given to thermal bridging and the issues that this can pose. The specification of rainscreen cladding and the accompanying fixing brackets can result in the potential for large thermal bridges where these fixings penetrate the insulation layer. These details require bespoke calculations in line with EN 10211 which some manufacturers will work alongside the designer to produce. In general, the flexible nature of stone wool slabs ensures that when tightly butted together they form a continuous layer eliminating gaps which could compromise performance, reducing another potential for thermal bridging.

Stone wool insulation by its nature may help improve the acoustic performance of the external envelope, capable of reducing unwanted external noise such as aircraft, weather, traffic noise or other external factors. As noise pollution increases, especially in towns and cities, the design of our buildings should adapt to maximise the acoustic comfort of occupants. It is well documented by the World Health Organisation that noise pollution has an impact on health and well-being. By incorporating stone wool insulation into the specification of the façade it is possible to limit further the sound that passes through the building envelope.

One key advantage that stone wool insulation products present over those with perhaps a better thermal performance is their fire classification. With the requirement in Building Regulations that in high rise and many larger buildings, products be either non-combustible or of limited combustibility, stone wool products make the obvious choice as they achieve an A1, non-combustible, reaction to fire classification.

Some products include additional features that may enhance their appeal to building designers. The ventilated gaps that are a feature of some rainscreen cladding systems can result in the underlying insulation becoming visible from the outside. The inclusion of a black glass veil on some insulation products can help to eliminate this aesthetic impact and ISOVER Polterm Max Plus is one of these.

Isover Polterm Max Plus is independently assessed and approved by the British Board of Agrèment (BBA) (19/5672) for specification in rain screen cladding systems and masonry overcladding systems over timber or steel constructions. Find out more about Isover Polterm Max Plus

If you’re ready to discuss your next project, contact our project specification team who can offer technical and product support.