Rendered expanded polystyrene is just as flammable when used as a cladding material as the aluminium composite panels which were found on the Grenfell and Lacrosse apartment towers, new tests show.
In its latest industry update, the Victoria Building Authority (VBA) released the result of fire testing of rendered expanded polystyrene (rendered EPS) for use as an external cladding material on commercial, multi-residential and public buildings.
It found that the material failed to meet requirements under the relevant standards (see update) and that its use as an exterior cladding material could result in the rapid spread of fire.
Indeed, when exposed to a large fire source, the material was found to be just as combustible as aluminium composite panels.
Just seven minutes into the full-scale test, molten flaming EPS was emanating from the test rig and flames were five metres above the combustion chamber.
“The rendered EPS (with fire retardant) in EIFS was deemed to have failed to meet the AS5113 EW classification acceptance criteria and failed to meet the BR135 classification. …” the VBA said.
“… The test results provide a clear indication that the use of rendered EPS (with fire retardant) in EIFS would result in a rapid vertical fire spread and pool fires when exposed to a large fire source, such as from a window opening or external source.
“Furthermore, it was concluded from the testing that rendered EPS in EIFS has a similar propensity for vertical fire spread to aluminium composite panels (ACP) cladding with 0% inert filler (commonly described as 100% polyethylene core) wall systems when exposed to large fire sources.”
The test relates to the performance of rendered EPS when used on external walls for ‘Class 2-9 buildings’ which are ‘of Type A or Type B construction’.
This includes commercial, multi-residential and public buildings such as apartment complexes, hotels/motels, office buildings, shops/retail buildings, car parks/storage buildings, laboratories and public buildings such as hospitals, schools and churches. It does not include Class 1 or Class 10 buildings such as detached houses, carports or sheds.
The test relates to buildings which are ‘of type A or Type B construction’, which refers to all buildings apart from those which have the least stringent requirements for fire resistance under Section C of the National Construction Code (NCC).
In light of the result, the VBA said any use of cladding which contains rendered EPS for these buildings will not meet deemed-to-satisfy requirements under Section C of the NCC.
Therefore, the material can only be used where a performance solution is applied and strict conditions are met including its use being approved by the Building Appeals Board (see update).
Widely used on external walls throughout the past twenty years, rendered EPS offers advantages in terms of its low cost, light weight, ease of installation and insulating properties.
When used on buildings, it is typically covered with render and has a similar appearance to rendered concrete.
On fire safety, however, viewpoints about its are varied.
On one hand, some argue that expanded EPS will perform satisfactorily during a fire because of its protective concrete render and/or because the material will melt rather than burn and propagate a fire.
Others, however, assert that the material contributes to the rapid spread of fire and that its use on Class 2 to 9 buildings represents an unacceptable risk.
Being a thermoplastic, polystyrene has a poor reaction to fire and may melt, shrink or ignite when exposed to elevated temperatures.
When it burns, a kilogram of polystyrene releases more energy than a litre of petrol.
Whilst chemical retardants can be added, the VBA says these do not prevent combustion from large fire sources and may at any rate leach over time.
As things stand, however, authoritative evidence about the performance of EPS in contributing to fire spread is scarce – a phenomenon the VBA says has contributed to greater risk of to public safety as not all building practitioners are aware of its dangers.
It advises occupants who are concerned about cladding on their building to speak with their building manager or owners corporation and cautions building practitioners to exercise caution when specifying, installing or approving external wall systems.
“Non-compliant use of combustible products in Class 2-9 buildings of Type A or B construction presents a major risk to the safety of building occupants,” it said.
“The removal and replacement of non-compliant cladding is costly and logistically difficult to undertake.
“Building owners facing the prospect of cladding removal from multi-unit apartment buildings can experience confusion, stress and anxiety.
“It is imperative that all building practitioners pay close attention when specifying, approving or installing external wall systems on Class 2-9 buildings of Type A or B construction. Regard must be had to current knowledge about combustible cladding, the type of cladding materials proposed, a holistic assessment of performance requirements in the BCA, compliance with the Act and Regulations and any ministerial guidelines or other orders.”
The tests were conducted by testing and certification firm Warringtonfire Australia and witnessed by the CSIRO.
The test was conducted in accordance with AS 5113:2016 Classification of external walls of buildings based on reaction-to-fire performance. This Standard sets out the procedures for the fire propagation testing and classification of external walls of buildings according to their tendency to limit the spread of fire via the external wall and between adjacent buildings.