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Sun July 22 2018

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New tests expose inadequacy of industry fire certification

25 Apr Research conducted on behalf of the insurance industry in the wake of the Grenfell Tower fire has exposed the ‘utter inadequacy’ of the laboratory tests currently used to check and certify the fire safety of building materials.

The cladding system used to refubish Grenfell Tower contributed to the spread and acceleration of fire
The cladding system used to refubish Grenfell Tower contributed to the spread and acceleration of fire

Now insurers are saying that if it burns at all, it shouldn’t be used in construction.

The Association of British Insurers (ABI) commissioned the Fire Protection Association (FPA) to carry out a series of controlled experiments recreating more realistic building conditions than those in which the standard tests are currently done. The aim was to measure what difference these factors could make in the event of a fire.

They found that real-life fires could burn at least 100 degrees hotter than previous tests suggest.

The real-life factors overlooked by the official testing regime include:

–    Test fires which are only made up of wood. In modern blazes, around 20% of the materials involved are plastic.

–     Cladding materials are sometimes tested as a sealed unit, whereas when fitted on a building they often include gaps, and cover a far more extensive area.

–    Materials are tested in an ‘as-manufactured’ condition, but during their actual use will often be pierced by vents or ducts.

The government commissioned former Health & Safety Executive chair Dame Judith Hackitt to review the building regulations in the wake of the June 2017 Grenfell Tower fire. In its submission to the Hackitt review, the ABI calls for an end to the use of all but non-combustible materials in construction, and a reformed testing regime that replicates real world conditions to provide genuine evidence of how materials perform in a fire.

Huw Evans, director general of the ABI, said: “Dame Judith Hackitt’s important work post-Grenfell has already recognised the building control system is broken. This latest research is yet more evidence that fundamental reform is needed to keep our homes and commercial premises safe from fire. It is a matter of urgency that we create the right testing regime that properly replicates real world conditions and keeps pace with building innovation and modern design.”

In one of the FPA tests, a section of wall and cladding was set up with a plastic vent installed – a common feature – and a fire started beneath the structure. Temperatures inside the vent indicated it was providing an almost instantaneous route for fire directly into the void between the wall and cladding, long before the time it would take fire to break through the outside cladding panels.

Fire safety, particularly in high rise buildings, often relies upon assumptions about how long it will take fire to penetrate certain areas of the building. The presence of fittings such as vents can make a big difference to how materials perform and how a fire will spread, and needs to be realistically modelled in testing, the FPA said.

Another issue that industry-standard tests fail to account for is that cladding materials are not always fitted as a sealed unit, which is how they are fire tested. On a building they often include gaps, and cover a far more extensive area.

The FPA started fires at the bottom of three columns. One had no cladding or cover at all, the second had cladding fitted to create a void but with sealed edges and ends, the third was clad with a void, leaky sides and some ventilation at the top and bottom.

On the open face, fire climbed 1.5 metres before burning out and self-extinguishing. The sealed cladding unit also saw fire climb a similar distance before it ran out of oxygen and self-extinguished. But the unit where the cladding had gaps rapidly caught fire up the entire six-metre height of the testing column.

This test demonstrated that the availability of oxygen makes a massive difference to how materials respond to fire, the FPA said. In well-ventilated voids, such as behind some cladding systems, the rate at which fire spreads can be greatly increased by a chimney effect. Any tests which restrict the availability of oxygen in a way that doesn’t happen on a full scale building will not be able to correctly assess how the materials will behave in practice, it concluded.

FPA managing director Jonathan O’Neill said: “The results of this important research confirm long-held concerns by many in the fire sector that the current cladding test standard requires urgent review to ensure that systems that pass are reflective of the systems that are installed and of the risks to which they are exposed. We urge BSI (British Standards Institution) to urgently reconvene the group responsible for this standard to consider the results of this research and to make changes to the standard as required.”

The research has been provided to Dame Judith Hackitt’s review.

Click here to read the research report in full.

 

 

 

 

 

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