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SAFETY & SECURITY
Although perimeter firestops are effective at inhibiting fire and smoke spread, compartmentation relies on them being able to maintain their fit between the floor slab and facade
combustible insulation that shields both the spandrel panel and the mullion can be used, alongside a perimeter firestop. This helps to preserve the integrity of the assembly and the stability of the curtain walling framing system, therefore allowing the firestop to perform its compartmentation function.
rigour, and usually involves reviewing product test data against appropriate standards and requirements, and submitting samples for analysis and comparison. Ad hoc factory visits and audits may also be carried out, and certification withdrawn, and re-testing required if any significant changes are observed.
Systematic thinking
The holistic approach to spandrel zone protection encouraged by standards such as EN 1364-4 also helps to better support fire and structural safety. While the UK regulations do not ask for passive fire protection beyond installing perimeter firestops and linear gap seals, in other jurisdictions such as the UAE, it is common practice to also protect the spandrel panel. Although perimeter firestops are effective at inhibiting fire and smoke spread, compartmentation relies on them being able to maintain their fit between the floor slab and facade. A part of this is being able to withstand movement, however, they also need to abut to a stable structure that can withstand elevated fire temperatures for a satisfactory period.
Aluminium mullions and transoms that are often used in non-fire rated curtain wall systems can deform in the high-intensity heat of a fire, jeopardising the structural integrity of the spandrel and the system. This can lead to gaps forming between the facade and slab edge, opening paths for fire, smoke, heat and gases to spread. To reduce this risk in aluminium systems, a fire-resistant board made of dense, non-
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Guidance & future developments The Association for Specialist Fire Protection (ASFP) has been recommending that linear gap seals used in curtain walls are “only tested to EN 1364-4” since 2014, and the Centre for Window and Cladding Technology (CWCT) announced in 2022 that it plans to update its guidance in Technical Note 98 to recommend that curtain wall fire stops should be tested in accordance with the standard. The proposed approaches are to use the firestop within the field of application of the test or within an extended field of application using EN 15254-6 to further widen the scope for approval. Additionally, in a recent consultation which closed on 17 March this year, the Government sought industry views on removing national classes from Approved Document B. The responses are still being analysed, but if this goes ahead, EN 1364-4 would become the only test path to compliance.
Going beyond
Curtain wall facades are complex, with their overall performance reliant on the interaction of many different components. Selecting complete spandrel protection systems, which have been developed and third-party tested as full-system solutions, can help projects go beyond regulation compliance, and thereby adequately safeguard the lives and livelihoods of people using the buildings for lifetime.
Chris Hall is external affairs director at Siderise
ADF OCTOBER 2023
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