14 COMMENT
By carrying out a ‘through-wall’ performance test, designers and contractors can have added assurance of the product's performance capabilities.
The through-wall concept
While there is currently no strict definition of what ‘through-wall’ means, it is widely regarded as the area from the inside face of the internal dry lining to the outside face of either the sheathing board or insulation. This part of the wall provides the majority of its fire, thermal and acoustic properties. The reason for the emergence of the ‘through-wall’ concept is that with so many exterior facade materials available, it would be impossible to test every possible wall construction. The ‘through- wall’ approach to performance allows manufacturers to test a meaningful number of material combinations (SFS, internal and external boards plus insulation). The tested solutions will either be from the dry lining through to the sheathing board or from the dry lining to external insulation.
This approach provides the design team with the freedom to choose the desired external facade, provided the necessary performance requirements are met.
Measuring performance
Building Regulations set out requirements for time performance, particularly with regard to integrity (passage of smoke and
Efficiency, versatility and sustainability count for little without certified proof of the system’s ability to meet the required technical performance standards
flame), insulation (temperature on the opposite side of the wall) and load bearing capacity where the wall is being used in a structural capacity. In order to achieve ‘through-wall’ fire performance data, SFS manufacturers construct different complete wall build-ups measuring 3 metres x 3 metres, comprising light gauge steel frames fitted with various combinations of boards and insulation materials to UKAS-accredited laboratories for testing. Each build-up is tested using a large-scale, high heat test (reaching up to 600°C in 5 minutes), which measures the performance of the whole wall by simulating fire trying to break out through a solid wall. Tests are conducted to British Standards BS EN 1364-1 and BS 476-22 (for non-loadbearing walls) to achieve the 120 minute, 60 minute and 30 minute fire ratings typically required by Building Regulations. In most cases, fire performance is an inside-to-out requirement, aiming to prevent the spread of fire from its source to adjacent compartments. Where buildings are in close proximity to each other, fire resistance will also be required from outside in. Whatever the circumstances, ‘through-wall' fire testing and the performance data it returns for the combinations of materials used in wall constructions is a positive step forward from SFS manufacturers. As more manufacturers commit to this approach, the array of certified wall constructions available to designers will increase – providing greater choice and flexibility in the solutions they can use. This will not only meet fire performance requirements but will also achieve other performance criteria – such as thermal and acoustic insulation – as well as meeting aesthetic and budgetary targets.
David Atkinson is specification manager for Metsec’s framing division
WWW.ARCHITECTSDATAFILE.CO.UK ADF OCTOBER 2021
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