Modern cladding approaches bring together a seemingly ever-increasing diversity of materials and components including fixings, fasteners and sealants. The manner in which these elements are designed, combined and integrated within a cladding system can have a significant impact on how it reacts to fire. For this reason, it makes sense to test the performance of complete cladding systems in their final configuration rather than assessing samples of each individual component in isolation.
Insurance-industry bodies, such as LPCB (Loss Prevention Certification Board) and FM Global, have used large-scale testing for a number of years as part of their various certification schemes. Importantly, the results from these tests are also backed by independent assessments of real fire scenarios involving insurer-approved insulated-panel systems with PIR-insulation cores.
Whilst the Building Regulations are primarily focused on ensuring occupants can safely exit a building in the event of a fire, insurer approval schemes have been designed to determine how well the building fabric will continue to resist fire spread after occupants have been evacuated, to preserve valuable property assets.
The two most widely recognised insurer standards for the fire performance of building-envelope systems in the industry are LPS 1181 from the LPCB and FM 4880/4881 from FM Approvals.
LPS 1181 Part 1
LPCB’s LPS 1181 Part 1 assesses the performance of roof and wall systems through a large-scale test. The test is designed to measure fire spread and is suitable for a range of building types. The complete system is installed within a 10m long x 4.5m wide x 3m high enclosure with an open front and ventilation window at the side. A large wooden crib is located on a steel table inside. One of the key performance requirements is that there shall be no sustained surface flaming beyond 1.5m from the perimeter of the crib in both horizontal directions on the walls and the ceiling. In addition, there are specific pass/fail criteria related to flashover, external surface flaming, burning brands from the ceiling, concealed burning and damage.
FM 4880 and FM 4881
FM Approvals is an internationally recognised third-party testing and certification service as part of FM Global, a worldwide insurance company that specialises in loss prevention. To achieve FM 4880 Class 1 Internal wall and ceiling panels without height restriction and FM 4881 Class 1 External wall panel systems without height restriction, products need to demonstrate that they do not propagate fire in a range of tests including small-scale material flammability tests and larger-scale system tests, which can include a 50ft corner test to establish the performance of insulated panel systems. The panels in these large-scale fire tests are installed in quantities and applications that replicate how they would be used in everyday field constructions. The results are then analysed to provide recommendations on limitations to the final application for which the wall and ceiling materials are FM Approved.
It is extremely important to note that both the LPS and FM tests detailed above are designed to assess the performance of specific systems in a fire, including the fixings and joints. The data provided is only relevant for the system tested and can’t be used to approve similar build-ups with alternative materials.
Insulated-panel case studies
Metal-faced insulated panels with rigid PIR cores are one of the most popular wall and roof system solutions in the UK and Ireland, and these systems can meet the rigorous testing of the insurance industry fire-performance standards. Independently researched fire case studies have proven the performance of insurer-certified PIR panel systems across the world, in different applications and different fire-related incidents.
They include a fire that occurred at Wharfedale Hospital in Leeds in 2003 while it was under construction. The building was steel-framed with concrete floors. The first and second floors had been covered with Kingspan PIR-insulated panels approved by LPCB to EXT-B of LPS 1181 Part 1. However, the ground-floor panels had not yet been installed, leaving the floor open-sided. It is thought the fire was started deliberately using adhesive which had been stored on the ground floor. The fire was discovered by on-site security, who alerted the fire service who brought the fire under control within 40 minutes.
The heat generated by the fire was significant. The concrete floor cracked and the steel beams, which had been protected with a fire-resistant intumescent coating, distorted. The fire service found light smoke but no fire-spread on the upper floors of the building. The independent report concluded that the PIR core of the insulated wall panels did not promote fire-spread.
Another telling example was a large fire that took place outside a furniture store in Slovakia. The fire source was a food cooking grill located 1.2m from the concrete-framed building, which was clad with insurer-approved PIR-insulated wall panels.
Fuelled by the contents of the grill and five propane gas cylinders, flames rose to over 10m and directly impinged the facade. During the 10-minute duration, the fire plume reached such a temperature that it melted the aluminium composite panel sign. The insulated panels directly impacted by the plume charred to a depth of 10mm. However, they did not propagate fire within the construction to areas remote from the flame impingement, and no evidence of smouldering or flaming combustion was found within the wall panels once the outer fire was extinguished.
Internally, the effects of the fire were limited to minor smoke ingress at panel joints with no direct fire ingress into the store. In fact, the effects were so minor that the store was able to reopen just 3.5 hours after the fire.
A series of 15 real fire case studies in a range of occupancy types has given similar conclusions demonstrating that PIR cores char, fire is not propagated within the core and there is no evidence to demonstrate that insurance-industry-approved panels increased the risk of fire spread.
It is critical that all fire-testing schemes are carefully evaluated against real-life performance. The independent case studies of approved insulated panel systems provide clear evidence that there is a very close correlation between the results of insurance-industry large-scale testing and actual building performance in real fires. Designers, installers and clients can therefore have confidence that approved products will perform as expected when installed following manufacturer guidance, securing both life and property.
For more information, go to www.kingspanpanels.co.uk