Fighting fire with fire

Insurers have been sceptical about the combustible nature of buildings incorporating composite panels. Mark Harris explains why they should be reassured

Holistic fire safety design and management is critical for every business and must involve a detailed review of every aspect of fire safety, including the internal and external structure of a building. It starts at the design stage, when products or systems with Loss Protection Certification Board or Factory Mutual approval should be used, and building regulations complied with. The process does not end at the design stage - just as important are issues of build quality and fire safety management of the finished facility. Knowledge of different types of panels and metal-cladding systems, their true design characteristics and whether they are used on the internal or external envelope, is also vital in assessing risk.

The complexity of fire safety and associated risk is further complicated by the wide variety of metal cladding products with inherently different fire performance characteristics. A fact not often appreciated is that performance is linked to installation, meaning the core material and the way the panels are fitted is of prime importance.

Having said that, awareness and understanding of these systems and their benefits is increasing and insurers are now much more involved in the specification process. Figures from a recent survey carried out for Kingspan by Lychgate Projects suggest that up to 30% of specifiers, contractors and clients have experience of insurers recommending or suggesting metal-cladding products or systems. Certainly, anecdotal evidence points to a sea change in the attitude of insurers towards the fire safety of insulated panels, with well-informed decisions being made by risk assessors.

Increased use

Insulated panels are widely used in the construction of 'sheds' - large industrial units and out-of-town retail buildings comprising steel structures clad in so-called sandwich or composite panels. Increasingly, these products are being used in the construction of hospitals and schools, mainly because they make for safer, faster construction and greater durability. More than half of the architects and their clients questioned for the survey said that ease and speed of construction were the key drivers to using composite panels. The research also suggested that the trend towards using them is set to continue, with the majority of architects and their clients expecting this to increase during the next two years, consistent with the actual market share trend in recent years.

Furthermore, a study by the Association of Building Engineers produced an accurate and robust fire brigade perspective on the issue of firefighting in buildings clad with composite panels. On questioning fire brigades in both metropolitan and rural areas about their policies towards firefighting in buildings with these panels, none questioned had a policy of 'no entry under any circumstances' into buildings where sandwich panels were present.

This refutes many of the assertions and fears previously expressed by insurers.

What all fire service personnel do insist on, however, is the understandable right to remain outside the building on fire if a dynamic risk assessment by the officer in charge at the scene dictates this as the most sensible course of action.

In the survey, the awareness of sandwich panels was high, with all fire brigades visited having a well-established policy on the subject. All those questioned emphasised the need to 'pre-plan' firefighting tactics, and there was evidence that each brigade endeavoured to gather information from fire prevention visits to premises.

The fire performance of expanded polystyrene (EPS), polyurethane (PUR) and polyisocyanurate (PIR) within such systems are very different. EPS is rarely, if ever, now used in external cladding, while external panels with a PIR core have achieved LPCB approval. LPCB-approved PIR core external panel systems have little or no influence on the outcome of fires, a fact borne out by several real fire case studies.

A critical step in clarifying the fire insurance risk was a technical briefing by the Association of British Insurers, which stated: "External claddings that are LPCB-approved to LPS 1181 can be regarded as satisfying the original grade two construction rules or be classed as a non-combustible building (Note: This grading does not imply that the material is non-combustible)."

By placing LPCB-approved external panels within the 'non-combustible building' category, the ABI endorses the view that LPCB-approved PIR panels will react as a non-combustible system in a fire. The classification also means that insurers' capacity to insure buildings clad in LPCB-approved panels is identical to those clad in other non-combustible systems, with no premium loading for the building owner or occupier.

Confidence in PIR panel performance as a non-combustible building element has been borne out in three serious fires: at a school in Rotherham; a hospital in Yorkshire; and a warehouse in Essex. In demonstrating the fire performance of LPCB-approved PIR panels, these fires also validate the LPS 1181 methodology as relevant to real building situations.

Fire spread prevention

In summer 2004, a serious fire took place in the roof void of Clifton Comprehensive School in Rotherham, six weeks before it was due to open.

LPCB-approved roof panels were exposed to an intense fire in an aerial walkway. The fire was investigated by Tenos, with input from South Yorkshire Fire Service, and it was clear not only that the panels played no role in fire spread but, in fact, played a key role in preventing fire propagation over a compartment wall.

The Tenos report recorded that the fire burned fiercely, with flames impinging on the blockwork walls and the partition above. The structural steelwork above the seat of the fire was severely deformed and the internal faces of roofing sheets in the immediate area of the fire had delaminated and deformed, exposing the insulation.

In spite of the substantial quantity of insulation exposed, there was no evidence that the insulation contributed to the spread of this fire.

The building contained many thousands of pounds of brand new computers and other equipment but, with the fire contained, there was no smoke damage to the equipment. The building opened on schedule - testament to the excellent fire performance of the cladding system.

A similar high level of performance was found at Wharfedale Hospital in Otley, which was the subject of an arson attack during construction.

Here a large pile of combustible building materials stored in the ground floor of the facility was ignited. The ground floor was open, with the external LPCB-approved PIR cladding starting at the first floor level.

An independent investigation by Tenos, with input from West Yorkshire Fire and Rescue, concluded that the external panels - although exposed to a large, rapidly developing fire - played no role in fire propagation or spread.

Perhaps the most challenging example was earlier this year, when LPCB-approved panels played a significant role in preventing fire spread to an adjacent building when fire devastated a large logistics warehouse operated by Eagle Global Logistics in Purfleet, Essex.

Although the fire completely burnt out the EGL building, panels on the adjacent building, only nine metres away, played an important role in preventing fire spread. The severe heat and flames generated by the burning building were so intense they burnt off the paint coating to the panels on the next-door building - and yet the PIR core did not ignite and no flames or smoke entered this building.

The EGL building itself was clad with a mix of LPCB-approved PIR panels with built-up systems on the walls and roof, possessing a mineral fibre core. An investigation by ACE Risk Consultants concluded that the PIR panels that formed part of the external walls did not play any role in the development and spread of the fire.

ID for safety

Initiatives that make life easier and save valuable time when insurers are identifying materials used within buildings have also been developed over the past few years. A key cause for concern has been the safety of firefighters dealing with a building on fire where composite panels have been used in the construction process.

Insurers and firefighters have, therefore, welcomed a new building labelling system from Kingspan which assists firefighters, insurers and surveyors in identifying its Firesafe insulated panels on both the external envelope and within buildings.

The weatherproof labels have been provided for more than 250 installations to date and the list is growing. The scheme provides an easy and simple way for insurance assessors, as well as firefighters arriving at a building, to identify immediately the type of insulated wall, roof and ceiling panels.

In the context of firefighting, this could be valuable data in informing the dynamic risk assessment process on site, although it is acknowledged that more needs to be done to raise awareness of the labelling scheme within fire brigades.

An additional system of markings printed in ultra-violet sensitive print has been in place for more than two years, which identifies all panels with the date and time of manufacture and the specification of the core insulator. The ultra-violet torches necessary to read them are provided free of charge to the fire service and insurers.

There is no doubt that insurers now have a much better and more accurate understanding of the performance of sandwich panel systems, and have played a key role in educating the wider market. Recent building fires show that LPCB-approved panel systems work well in real fires and support the view that these cladding systems can be classified as 'non-combustible building'.

Building and panel labelling can give further confidence that the situation is being well-managed, but ongoing dialogue between insurers, certification bodies, fire brigades and panel manufacturers is key to ensuring that the correct choice of panel results in the optimum outcome. With a plethora of evidence and case history to inform the fire safety debate, it seems insurers have a right to be reassured on the subject of composite or insulated panels.

METAL-CLADDING SYSTEMS EXPLAINED

Sandwich panels used for external envelope

- Panels manufactured off site, cut to length and delivered for fixing to the structural steelwork of the building.

- Built-up system used for external envelope

- Multi-component systems fabricated on site.

Sandwich panels used in internal walls

- Used particularly in food manufacturing, pharmaceutical manufacturing and clean rooms.

- Mark Harris is fire services engineering director of Kingspan Panels.

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