Flame-retardant Henkel adhesives used on A2 spandrel panels
15 August 2021
SPEEDPANEL, PART of the Speedclad group of businesses, has developed a range of insulated composite spandrel panels that they company says provides both extremely quick building encapsulation and fire-retardant properties in accordance with the latest regulations.
Notably, the company worked in close liaison with adhesive expert Henkel to identify the optimum flame-retardant bonding product for the panels. In a construction market still reeling from the tragic Grenfell Tower fire in 2017, the resulting Speedpanel A2 Glass and Speedpanel A2 Aluminium carry an independently certified fire rating of A2-s1 d0, creating a huge USP for the company and opening up vast market potential in both new build and replacement façade projects.
“Unfortunately, many spandrel panel manufacturers still state that their products are fire-rated to A1 as they make their products from A1-rated materials,” says Fraser Brown, Regional Director at Speedclad. “In truth, however, once these materials combine to form a composite panel, any individual material fire rating doesn’t mean the A1 rating still stands”
Speedpanel insulated composite panels use adhesives to bond various materials together. However, achieving the required A2-s1 d0 fire rating for the panel is challenging as many adhesives feature solvents, isocyanates or PVC, all of which are highly flammable.
“For this reason, we opted to partner with Henkel, to develop a panel construction using a flame-retardant adhesive,” states Fraser. “As a result of our collaboration we now have a suite of industry-first aluminium and glass-faced spandrel panels that have been independently tested by Warrington Fire to achieve A2-s1 d0, in accordance with BS EN 13501-1 2018, thus giving specifiers, clients and contractors complete peace-of-mind. Moreover, compared to fitting a conventional double-glazed unit - with its supplementary insulation and associated framework - Speedpanel is far quicker.”
In November 2018, the Government announced changes to Regulation 7 of the Building Regulations in order to ban the use of combustible material in the external walls of certain high-rise buildings in England. The newly introduced Regulation 7(2) states: “Building work shall be carried out so that materials which become part of an external wall, or specified attachment, of a relevant building are of European Classification A2-s1 d0 or Class A1 classified.”
Generally all materials should comply with a minimum fire classification of A2 s3 d2. However, if a building falls within the ‘relevant building’ class, this fire classification is redundant and all materials need to be A2-s1 d0 rated, effectively a higher level of classification. ‘Relevant buildings’ include residential and institutional buildings that are more than 18m high.
“Making a non-combustible product that complies with A2-s1 d0, particularly one that relies on adhesives, is a tall order,” says Fraser. “We have only managed to overcome this difficulty by working in partnership with expert companies like Henkel.”
In terms of composition, Speedpanel A2 Glass features a steel rear tray, an insulated (mineral wool) core, a proprietary interlayer and a glass front face that is available in the full grey scale from white to black. The same composition applies to Speedpanel A2 Aluminium (powder coated or anodised in a wide range of colours), minus the specialist interlayer. Any composite panel built of several materials and sold as a single panel - even if the materials are individually A1 fire-certified (as is the case with Speedpanel) - will require re-certification as the complete panel.
“We initially considered mechanically fixing the front and back trays using non-combustible fasteners, although this was dismissed due to the negative impact on thermal bridging and the potential for condensation issues,” explains Fraser. “As a result, we chose adhesives to bond the components together, but there were many challenges to overcome beyond just being flame-retardant.”
Although heat-soak-tested toughened glass is up to five times stronger than normal glass, a particularly heavy impact can force it to shatter into thousands of tiny ‘pebbles’. It is the cracks between these pebbles that create stress on the adhesive, which means the glass could potentially fall from the building.
“We wanted to create a product where this outcome could not occur; where the glass would remain in place even in the unlikely event of a heavy impact,” says Fraser. “I’m pleased to say that our partnership with Henkel and the extensive adhesive trials helped us to meet this objective. A2-s1 d0 classification is really important, but so is glass retention.”