Variations in test regimes for curtain wall slab edge compartmentation across the globe
To prevent fire spread through the void between the floor slab edge and spandrel panel, known as the movement or perimeter joint, there must be a continuation of fire resistance of the compartment floor right up to the façade using perimeter firestopping measures. Many codes and regulations around the world make provisions for this, requiring the use of slab edge fire seals that have had their fire resistance certified to different product test standards. However, the test paths to compliance offered can vary hugely in scope, and the types of curtain walling systems they can apply to.
It is important that designers, specifiers, and fire engineers appreciate the variances in the scope of these tests for a more holistic understanding of the firestopping measures installed within the spandrel zone and to ensure the highest levels of fire safety are achieved. This is especially important as most commonly used curtain walling systems are non-fire rated with aluminium framing and non-fire-resistant vision glazing, and in situations where there is no requirement for fire resisting protected spandrels, floor slab projections or minimum vertical height separations between window openings.
In this blog, we explore ways to approach testing of these crucial products and give a quick overview of the most widely used fire test standards.
Please note that whilst these test standards have been developed by standard bodies in specific jurisdictions, these are referred to around the world as ways of determining the performance of perimeter fire seals for curtain wall façade systems.
The component approach
In some countries, test approaches that focus on the fire resistance performance of the specific material used as the perimeter fire seal is considered enough to demonstrate compliance – even though it’s not always best practice, for example:
BS 476-20
BS 476-20: 1987 - Fire tests on building materials and structures. Method for determination of the fire resistance of elements of construction (general principles) is still currently an accepted legacy test path to compliance under some statutory compliance guidance documents used in the UK e.g. Approved Document B: Fire Safety (England and Wales). However, now officially recognised as being outdated by England’s government it is due to be withdrawn on 2 September 2029. This is a small-scale, static test that requires a specimen to be installed between two concrete lintels within a furnace and subjected to defined heating and pressure conditions.
Whilst BS 476-20 can provide 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 perimeter firestop’s ability to resist fire in its intended application. Therefore, it is advisable to consider it as part of a wider and more comprehensive program of testing which would allow a much broader analysis.
AS 1530.4 and EN 1366-4
AS 1530.4: 2014 - Methods for fire tests on building materials, components and structures – Fire-resistance test of elements of construction, and EN 1366-4: 2021 - Fire resistance tests for service installations - Part 4: Linear joint seals are similar in nature to BS 476-20, in that they test specimens in static form between concrete slabs. EN 1366-4 however, is a little more onerous than AS 1530.4 in terms of the furnace heating regime measurement because of the difference in furnace thermocouples used. This similarity often leads to products imported into Australia and New Zealand being classified in accordance with AS 1530.4 without being tested to the standard itself but instead using EN 1366-4 test data.
Nonetheless, whilst, EN 1366-4 specifies a method for determining the fire resistance of linear joint seals based on their ‘intended end use’ the standard itself explicitly states, “perimeter seals of curtain walling are excluded from this part of the EN 1366 series.”
This is further underpinned by the Association for Specialist Fire Protection’s (ASFP) Advisory Note 7, which states “test evidence obtained using BS EN 1366-4 cannot be used to support that end-use application” - i.e. perimeter edge seals in curtain walling applications.
As such, whilst comparison reports classifying the fire resistance level (FRL) of products manufactured outside of Australia to AS 1530.4, based on EN 1366-4 test data, may gain market acceptance in Australia, it cannot be deemed best practice.
The system approach
Whilst perimeter seals are extremely effective at inhibiting fire and smoke spread, compartmentation is reliant on them being able to maintain their fit between the floor slab and façade. This is why many regions look toward standards that offer a much more holistic perspective of the perimeter seal’s fire resistance performance in the context of a realistic spandrel construction, rather than its performance as a standalone product. Here are some of the mostly commonly referred to test standards that take this approach:
EN 1364-4
EN 1364-4: 2014 – Fire resistance tests for non-load bearing elements (Curtain walling – part configuration) is widely referenced in building codes and regulations in many countries and is the recommended test standard for curtain wall perimeter seals in the Association for Specialist Fire Protection’s (ASFP) Advisory Note 7, with the Centre for Window and Cladding Technology (CWCT) also announcing a proposed update to its Technical Note 98, recommending that curtain wall perimeter edge firestops should be tested in accordance with this standard. It looks at the spandrel assembly of a curtain wall system, comprising the mullions, transoms, and infill and spandrel panels. There are specific configurations of the test that can be chosen depending on the primary element that needs to be assessed. In very simplified terms, Configuration 5 is used to assess the ability of the perimeter fire seal to contain the fire inside the compartment, under the stress of temperatures and pressures that lead to in-test deflection of the façade and floor slab.
It is important to note that EN 1364-4 also includes provision for long-term façade movement by referring to the European Technical Approval Guidelines 026-3, which is now superseded by European Assessment Document (EAD) 350141-00-1106. This requires that the perimeter seal is subjected to a minimum of 500 cycles between the minimum and maximum joint width, to simulate wind sway, seismic activity, and thermal load at a rate designated by the test applicant 24 hours before fire exposure. If manufacturers are voluntarily applying a CE Mark to their slab edge products, it is vital to understand whether they have been tested in accordance with EAD 350141-00-1106 as only in these cases has true cyclic movement testing been applied.
ASTM E2307
ASTM E2307, Standard Test Method for Determining Fire Resistance of Perimeter Fire Barriers Using Intermediate-Scale, Multi-story Test Apparatus measures “the performance of the perimeter fire barrier and its ability to maintain a seal to prevent fire spread during the deflection and deformation of the exterior wall assembly and floor assembly during the fire test.” It uses intermediate scale multi-storey apparatus to better replicate a fully developed curtain wall fire. The perimeter seal is exposed to fire from both inside and outside the test compartment to simulate the room where the fire started, as the fire plume exits the room of fire origin through a window opening and attempts to leapfrog to the next floor. It also includes provisions for pre-cycling, or ‘cold’ movement before the test begins, covering thermal load, wind sway, seismic movement, and all these combined.
ASTM E2874
ASTM E2874 Standard Test Method for Determining the Fire Test Response Characteristics of a Building Spandrel-Panel Assembly Due to External Spread of Fire Using Intermediate-Scale, Multi-story Test Apparatus looks more specifically at assessing the spandrel assembly’s resistance to fire spread and the leapfrog risk. It has been designed to emulate a fire scenario at post-flashover stage inside a compartment. It analyses the ability of the spandrel assembly to prevent fire from spreading over the façade exterior to a room’s interior on the floor above the compartment of origin. The test specimen includes the exterior wall spandrel panel assembly, fasteners, structural supports, and any glazed openings. When applied in conjunction with ASTM E2307, this can provide a uniquely rounded view of how both the perimeter fire seal and the spandrel insulation can achieve complete compartmentation, preventing fire from spreading floor to floor both internally through the curtain wall system and externally up its surface.
IS 18190
The Indian standard, IS 18190: 2023 - Fire Resistance of Perimeter Fire Barrier Joint System released in June 2023 by the Bureau of Indian Standards (BIS) references ASTM E2307, as well as UL 2079 – Tests for Fire Resistance of Building Joint Systems. This test not only looks at the fire resistance of the perimeter fire barrier joint, but also assesses the integrity of the spandrel panel above the perimeter firestop for up to 120 minutes. In addition, the test calls for the assessment of the L-Rating / Air-Leakage rating of the perimeter fire seal. The IS 18190: 2023 mandates adherence to the ISO 834-1 time-temperature curve for evaluating the perimeter fire barrier joint system, which is the same time-temperature curve followed by EN 1363-1 and subsequently used within testing to EN 1364-4. Again, like the other tests, it also requires pre-test movement cycling to simulate the dynamic movement of the barrier.
Third-party certification
Whatever the route and test standard, it is highly recommended 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 is a rigorous process, usually involving reviewing product test data against appropriate standards and requirements, submitting product samples for analysis and as comparative samples. Factory visits and audits may also be carried out randomly, and certification withdrawn, and re-testing required if any significant changes are observed.
Best practice, better curtain walls
Choosing curtain wall perimeter seals that have had their performance verified with testing that reflects their end use in the ‘as-built’ condition can not only enable compliance in many jurisdictions but also encourage best practice and, where possible, help to go beyond regulatory requirements to deliver enhanced spandrel protection. Additionally, products that are proven to perform consistently across differing standards in myriad system configurations can be considered far more reliable than that of their one-test ad-hoc counterparts, offering peace of mind that they will perform as intended in the event of a fire—all which contribute to safer curtain walled buildings around the world.
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