Spandrel panels span the vertical distance from the top of a window and the lower sill of the window in the next storey above.
“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 panel manufacturer 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 – which the company has now achieved for both aluminium and glass -- is challenging, it says, as many adhesives feature solvents, isocyanates or PVC, all of which are highly flammable.
Those materials have been outlawed since the November 2018 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) requires materials certified to A2-s1 d0 or Class A1. In addition, materials need to be certified to A2-s1 d0 if a building falls within the ‘relevant building’ class, which includes residential and institutional buildings that are more than 18m high.
PRODUCT STRUCTURE
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. 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 Brown. “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 strong 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.
Brown continues: “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.”
Describing the R&D approach of Henkel (01442 278000), he adds: “The research was two-fold, in terms of identifying which adhesive from the Henkel portfolio would best suit our needs for both fire classification and grab strength. It succeeded on both counts.”
In fact, Henkel supplies Speedpanel with two types of adhesive for different bonding tasks within the Speedpanel A2 Glass and Aluminium products. Henkel has also made proposals in terms of suitable application methods that would optimise adhesive quantity and delivery speed: everything from automated spraying to simple pour-and-spread.
