Sandwich panels comprising two metal facings and a polyisocyanurate (PIR) rigid foam core have been used for years to thermally insulate large warehouses, cold stores and other industrial buildings.
But now, engineers at Bayer MaterialScience have developed a more environmentally compatible PIR foam that they claim has clear benefits over established systems, especially in terms of the smoke it develops when burnt.
Metal-faced sandwich panels based on the new product have been shown to achieve a B-s1,d0 classification in the DIN EN 13823 Single Burning Item (SBI) test, with s1 representing the lowest class of smoke that is developed and d0 indicating that no flaming droplets are produced.
In recent years, the SBI test has become a standard requirement in Europe for the fire and smoke behaviour of building components. For example, the new European standard for sandwich panels – DIN EN 14509 – also uses SBI-based tests for fire classification purposes.
PIR metal-faced sandwich panels can be manufactured on continuous laminators. The PIR reaction mix is first laid down on one metal facing. It foams and immediately bonds with the second facing, which is applied from above. In this way, the rigid foam core is bonded to the two facings in a shear-resistant manner. The finished sandwich panels are self supporting, strong and relatively light.
’The B-s1,d0 classification enables our customers to undertake construction projects that are subject to stringent requirements in terms of components’ fire and smoke behaviour and where it was previously essential to use inorganic core materials based on mineral wool to achieve smoke class s1,’ said Harald Wolf, head of marketing for the Europe, Middle East and Africa (EMEA) region at BaySystems Insulation. ’The new development creates an additional market segment for polyurethane-based metal-faced sandwich panels.’
Dr Rolf Roers, who is responsible for metal composites in Bayer MaterialScience’s applications engineering division, added: ’It goes without saying that the PIR core is not the only factor enabling this classification to be achieved in the SBI test. The sandwich panel must also have an appropriate joint structure. Nevertheless, tests have shown that a B-s1,d0 classification is possible if the chemical composition and panel structures are ideally matched.’
The insulating effect of PIR foams is much better than that of mineral wool. For example, a 10cm-thick layer of PIR has a heat transfer coefficient of around 0.25W/m2K, whereas the value for equally thick mineral wool insulation is normally just 0.4W/m2K.
A rough estimate of what this difference means in terms of energy consumption can be made based on the example of a factory building. ’Assuming a building has a floor area of 40 x 20m2 and is 10m high, the annual amount of heating oil saved could be roughly 3,000 litres if both the walls and the roof are insulated with PIR metal-faced sandwich panels, rather than panels of the same thickness based on mineral wool,’ said Roers.