Comparing Insulation Cores used in Sandwich Panels

9 June 2019 Kingspan MEATCA
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You might already know that sandwich panels are a game-changer when it comes to constructing fireproof and weatherproof building envelopes with the right insulation properties. Yet with so many types of sandwich panels available, it might be hard to choose the best one for your project. Here, we take a brief look at the variety of sandwich panel insulation cores out there, focusing on the most frequently used materials and how they perform under different conditions.
One of the materials commonly used in insulation cores is EPS (expanded polystyrene) and on rare cases XPS (extruded polystyrene) is also used as an option. Both synthetic thermoplastic polymers made from styrene, EPS and XPS form a lightweight rigid foam. The slightly greater density of XPS makes it stronger and more durable compared to EPS insulation cores. The thermal conductivity of EPS, is around 0.038W/mK. Indicated as the lambda (λ) value, this figure is closer to 0.033W/mK for XPS, meaning it offers slightly better thermal performance compared to EPS. EPS and XPS offers very poor fire performance, as both materials begin to soften instead of charring when exposed to fire.  In terms of moisture protection, XPS resists moisture ingress and mould growth better than sandwich panels with EPS insulation cores.
The second group of insulation cores used in sandwich panels are made of mineral wool, in the form of stone wool specifically. These materials are manufactured by melting stone and later spinning them into wool-like fibres. The main feature of the stone wool panels is their “non-combustibility” which makes them have excellent fire protection performance. However, their typical thermal conductivity performance is the poorest compared to all the other core types with lambda (λ) value ranging from 0.03-0.043W/mK. This results in stone wool panels to be produced in almost twice the thickness of PIR panels to achieve the same U value which results in reduction of built-up space in properties. Due to their fibrous structure, mineral wool panels are also required to be produced in very high densities (typically 100kg/m3 & above) in order for them to be structurally stable thus resulting in very heavy and thick panels which are difficult to transport and install on-site. Lastly, due to their open cell structure, mineral wool panels can also absorb water and are susceptible to mould formation in a moist environment and water will significantly degrade thermal performance.
Last but not least, another pair of materials that are frequently used in the insulation cores of sandwich panels are PUR (polyurethane) and PIR (polyisocyanurate). Both are thermosetting rigid foams that won’t melt.  It is important to note that descriptions ‘PUR’ and ‘PIR’ encompass a range of differing formulations.  The fire performance of PUR tends to be poor and the only reliable way of understanding the fire performance of PIR is to test the panel systems in a full scale test such as those used by the insurance industry (FM & LPCB).  It is only through realistic large scale testing that the performance of PIR core panels systems can be accurately assessed. Overall, both PUR and PIR offer excellent thermal properties, with lambda (λ) values typically around 0.023W/mK for PUR and 0.020 – 0.022 W/mK for PIR. Although both PUR and PIR form a char instead of melting when exposed to fire, sandwich panels with PIR insulation cores that have insurance industry certification offer greater fire performance. In terms of moisture resistance, both PUR and PIR perform well owing to the closed-cell structure of the insulation.

Thermal Comparison2
With so many materials to choose from, each with its own advantages and disadvantages, it’s crucial that construction professionals select the best option for their projects. Thankfully, with technological advances and investments in R&D efforts, the world’s top building envelope providers are constantly improving their range of products to perform well across the board. One such innovation is the QuadCoreTM Technology offered by Kingspan, which is a hybrid insulation core technology to deliver superior thermal performance and fire protection. The lightweight and closed-cell structure of QuadCoreTM gives it a class-leading thermal conductivity value of 0.018W/mK. Thanks to extensive fire testing and certifications, QuadCoreTM panel systems have been tested and certified to a range of standards that include FM approval to FM 4882 for use in smoke sensitive occupancies such as pharmaceutical manufacturing and storage.  Quadcore panel systems are weatherproof, resisting moisture and mould to retain the specified level of insulation performance for the duration of the building’s lifetime. With additional enhanced environmental credentials and a 40-year thermal and structural performance guarantee, QuadCoreTM offers the best of all worlds for designers, architects and builders everywhere.