SAFETY & SECURITY 73
Going beyond fire compliance C
urtain wall systems are typically constructed with a gap between the facade and the floor slab to allow
for building movement, with the addition of a fire seal solution to ensure passive fire safety. However, with two ‘test paths’ to compliance available, it is vital for specifiers to understand the accuracy of standards on the real-life performance of products.
The two ‘test paths’
Approved Document B (England and Wales), Technical Handbooks Section 2 (Scotland) and Technical Booklet E (Northern Ireland) all offer two test paths to compliance for the fire resistance of perimeter firestops. These are, firstly, BS 476-20 – ‘fire tests on building materials and structures – method for determination of the fire resistance of elements of construction (general principles)’. The second is EN 1364-4: 2014 – fire resistance tests for non-load bearing elements via classification standard EN 13501-2. The significant differences in scope, methodology and evaluation mean that these two paths are not equivalent, and choosing which test method is the most appropriate will depend on the real-world demands of the application.
Product vs system Published in 1987, BS 476-20 is a small- scale, static test that requires an insulation product to be installed between two concrete lintels within a furnace and subjected to defined heating and pressure conditions to establish its fire resistance (integrity and insulation) rating. While it offers a basic understanding of a product’s standalone performance, the test is designed to be generalised and therefore cannot give a clear indication of a product’s ability to resist fire in its intended application. By contrast, EN 1364-4 is a ‘part configuration’ test that applies to ‘Type A’ non-fire-rated, and the less commonly used ‘Type B’ fire-rated, curtain walls. It
ADF OCTOBER 2023
examines the resistance to internal and external fire exposure of the complete spandrel system for the test duration; (including the spandrel panel, perimeter fire seal, fixing of the framing system used to attach the curtain walling to the floor, or combinations thereof.) The test’s wide scope means it can be used for different kinds of curtain walling constructions.
This systemised approach is much more reflective of a true spandrel construction, especially where the test assembly is also subjected to movement cycling (in accordance with EAD – European Assessment Document - 350141-00-1106) before fire testing.
The EAD requires that the perimeter fire seal is subjected to a minimum of 500 cycles between the minimum and maximum joint width, to simulate wind sway, seismic activity and thermal loads, at a rate designated by the test applicant. It is not compulsory, but it is required for CE marking when claiming a >7.5% movement capability, and there are only a select number of perimeter firestops on the market which have been tested and certified to this EAD.
Such testing is crucial to demonstrate that the perimeter firestop is capable of withstanding in-application deflection and dynamic movement without degrading, and thereby able to maintain its ability to achieve the required fire resistance over the building’s life. The results offer a clearer understanding of the fire resistance in terms of not only how the perimeter fire seal will perform as a product, but also how it will interact dynamically with other components of the spandrel under fire conditions.
Third party assurances Whatever the route and standard used, it is advisable to validate fire test data with third-party certification from an accredited body, to provide confidence in the performance and consistency of the products. Gaining certification requires
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Siderise’s Chris Hall asks whether an approach of merely complying with regulations in specifying passive firestopping in curtain wall systems is good enough, or if specifiers should be looking to other standards
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