Phil Marsh, Product Manager at Speedpanel discusses façade remediation and building envelope retrofit projects becoming increasingly commonplace as we look to bring our current building stock in line with the updated fire safety regulations, as well as address the need for a more energy efficient and aesthetically sensitive built environment.
Where these projects feature a curtain wall system, an essential element to consider is the spandrel zone. Spanning the space between the vision glass, this area presents a number of challenges and, by selecting the right spandrel solutions early, designers can streamline specification and support a swifter, higher quality installation.
Regulatory requirements for curtain wall spandrel panels
All nations of the UK recognise the importance of ensuring that external wall systems used on high-rise, high-risk buildings are made from materials which do not enable fire spread.
In line with Approved Document B: Fire Safety under B4 External Fire Spread Regulation in England and Wales, and Northern Ireland in line with Technical Booklet B: Materials and Workmanship, external walls of ‘relevant buildings’ are required to be constructed with materials achieving European Class A1 or A2-s1,d0 (i.e. be non-combustible or of limited combustibility) in accordance with EN 13501-1 (Reaction to Fire). This includes non-vision window spandrel panels.
Using the definition from ADB, a ‘relevant building’ is defined as one “with a storey at least 18m above ground level (not including roof-top plant areas or any storey consisting exclusively of plant rooms), which contain one or more dwellings, an institution, or a room for residential purposes”. The exact building types defined vary region-to-region and are often updated, so should always be cross-referenced with the most recent relevant building regulations.
In addition, residential buildings between 11-18 metres in England must also be constructed with materials achieving European Class A2-s1,d0 or above, or their external wall systems must meet the performance criteria given in BR 135 for external walls using full-scale test data from BS 8414-1 or BS 8414-2.
In Scotland, Technical Handbook Section 2: Fire for domestic and non-domestic buildings states that the external walls on all buildings with a storey at a height of more than 11m, and certain assembly, entertainment, hospital, and residential care buildings below 11m must be constructed using Euroclass A1 or A2 rated materials (no “s” or “d” rating mentioned).
Therefore, applicable remediation or refurbishment projects – regardless of region – must use spandrel panels that achieve either an A1 or A2-s1,d0 in accordance with EN 13501-1.
Spandrel panel solutions
There are two main types of spandrel panel options. Traditional spandrel panels are built-up on site with a back sheet, insulation core and a face panel which are cut to size each time for every panel. In addition to requiring much more labour and skill to fit correctly, this panel-by-panel approach can also lead to variations in size, fit and quality which could potentially compromise the project’s overall fire performance.
To resolve this, modern composite panels are now available which combine internal and external facings, core insulation material, tray, and other components into a single, pre-engineered unit which can be tested as a complete solution, and can be applied consistently across multiple floors and projects.
It is important to note that, whatever solution is chosen, creating an A1-rated spandrel panel presents a challenge due to the need for adhesives which bind components together. Whilst some products use mechanical through-fixings between the front and rear surfaces, these can often offer a route for thermal bridging, compromising the thermal integrity of the panel and the wider facade. Therefore, specialist adhesives in panels achieving A2-s1,d0 certification are often preferred as a more holistically performing solution.
Pre-insulated composite spandrel panels and compliance
The biggest advantage of using a pre-insulated composite spandrel panel is the fact that the whole solution can be tested to in accordance with EN 13501-1 Reaction to Fire. Some built-up spandrel solutions claim to be A1 or A2 rated due to the performance of their individual component parts. However, this does not take into account the potential interactions of the various elements within the spandrel solution or the inclusion of adhesives – as explained above – in the event of fire, and therefore is not reflective of the real life fire performance of the complete system. Selecting a composite spandrel panel with a single test certificate that applies to the entire unit can help to guarantee compliance and streamline specification.
This ‘single-product’ solution can also help to ensure consistent and replicable installation quality across the whole building. Tolerances are often tight in existing facades undergoing refurbishment or remediation, as new units replace substandard or non-compliant panels, and there can often be tens or hundreds of spandrel panels across the elevations. It is vital that each new spandrel panel delivers a consistent level of performance to ensure building-wide compliance.
Some pre-manufactured composite spandrel panels are also engineered to be very rigid too, using folded returns along the edges of both the front and rear trays. The result is a more robust panel than would be the case with panels made up of flat front and rear sheets. This, along with folded corners, provides a much more precise and accurate end result, ensuring the front and rear trays line up during the manufacturing process, keeping tolerances tight and profiles consistent.
Onsite benefits
Pre-insulated spandrel panels are designed for ease of installation. They can be simply glazed into the facade as whole units, requiring no complex onsite assembly. This helps to reduce installation time for project facades, lessening the amount of time needed to work at height and the disruption to building users, whilst also ensuring consistent fire performance and thermal integrity.
As an external wall product, it is also important that they meet the aesthetic aims of the project – whether that is to maintain the existing appearance of the building or deliver a new look. Composite spandrel panels come in a range of aesthetic options, with aluminium and non-vision glass faced options available in an array of colours and finishes that are designed to withstand inclement weather and unexpected impacts.
Panels in practice: Citispace Leeds (2022)
The thriving mixed-use city centre complex, Citispace Leeds, is home to over 300 apartments, shops, and shared spaces. However, due to a number of non-compliant elements, remediation work needed to be undertaken under the Building Safety Fund (BSF) scheme. This included replacing 460 spandrel panels to ensure compliance with current fire safety regulations.
Speedpanel A2® Glass provided an ideal solution. This is a pre-manufactured, pre-insulated glass spandrel panel, comprising a steel rear tray, an inner non-combustible insulated core, non-combustible hard edging, and a visually striking, impact resistant glass face (tested in accordance with the TN 75 Hard Body Impact Test). Made possible by Speedpanel’s glass retention system, it works to absorb impact energy to retain glass pebbles in the event of an impact, keeping those below safe from falling fragments.
Specified in a bespoke 31 mm thickness to match the existing spandrel panels, designers chose a ceramic-coated Jet Black finish to match the project’s existing facade look whilst offering a high level of fire performance. To ensure the tailor-made panels still achieved the essential A2-s1,d0 classification, Speedpanel’s technical team put the product through a whole new set of independent testing and extensive pre-production calculations.
The installer’s Project Lead recounted that:
“Speedpanel A2® allowed for quickness and reduced disruption whilst replacing panels in under floor areas – our installers could complete large areas without damaging existing furnishings or needing to handle lots of material on site. By glazing directly into the existing curtain walling system, the Speedpanel A2® spandrel panels were able to be installed swiftly and manufactured to fit in a range of rebate depths to suit these older facades”.
The factory-engineered composite spandrel panels ensured consistent quality and enabled quick and simple installation directly into the existing curtain wall system, with no need to build up the various layers of the product.