First of all, I would like to express my deepest condolences to all victims and their families of the fateful fire at Grenfell Tower in London. This type of tragedy never has a single cause, it is convenient to analyse all of them due to fire safety is complex.
As consequence, the government of the United Kingdom established a Building Safety Programme, with the aim of ensuring high rise residential buildings are safe and residents feel safe in them.
Among other actions, a series of tests have been carried out with specimens of cladding products made with aluminium composite and usual in many of these buildings (hereinafter ACM: Aluminium composite material).
The English laboratory BRE has carried out 7 large scale tests according to BS 8414-1 to determine if the use of an ACM as a component of a façade system in a high-rise building (more than 18 m in height) is safe following the guidelines set by the current regulation in England. The specimens tested corresponded to cladding system with a ventilated cavity.
Below it is shown a summary table of the products that make up the test specimen and the results obtained. All specimens tested contain stone wool vertical and intumescent horizontal cavity barriers.
- PE: Polyethylene
- PIR: Polyisocyanurate foam insulation
- SW: Stone wool insulation
- PF: Phenolic foam insulation
The classification criteria are those shown in BR 135:2013 (Fire performance of external thermal insulation for walls of multistorey buildings, third edition):
- External fire spread
- Internal fire spread
- Mechanical performance
Once the results of the BRE tests are known, a number of recommendations have been issued to building owners who have the materials tested or similar. These recommendations will depend on the results obtained:
Wall systems which failed the test:
- It is recommended that building owners implement interim mitigation measures for ensuring the safety of residents.
- Building owners should take professional advice. This professional advice may be obtained from a qualified chartered professional with relevant experience in fire safety, including fire testing of building products and systems.
- Building owners will need to take professional advice to ensure that any remedial work is undertaken safely and to ensure any replacement materials are safe.
Wall systems which passed the test:
Take professional advice on whether any remedial work is necessary to ensure the safety of their building. If any remedial work is undertaken building owners will need to take professional advice to ensure that work is undertaken safely. Assure themselves that remedial work also complies with Building Regulations guidance on how the system is designed and fitted – including provisions for fire breaks and cavity barriers.
Following full scale test, the Department for Communities & Local Government has published the conclusions of the Expert Panel’s advice.
- ACM cladding with unmodified polyethylene filler with PIR foam insulation and with stone wool insulation (test 1 and test 2 respectively)
These wall systems both failed the test, which means they did not adequately resist the spread of fire over the wall to the standard required by the current Building Regulations guidance and which is set out in BR135. Based on these test results, the Expert Panel’s advice is that, they do not believe that any wall system containing an ACM with unmodified polyethylene filler, even when combined with limited combustibility insulation material, would meet current Building Regulations guidance, and are not aware of any tests of such combinations meeting the standard set by BR135. Wall systems with these materials therefore present a significant fire hazard on buildings over 18m.
- ACM cladding with fire retardant polyethylene filler with PIR foam insulation, phenolic foam insulation and stone wool insulation (test 3, test 7 and test 4 respectively)
The tests with PIR foam insulation and phenolic foam insulation both failed the test, which means they did not adequately resist the spread of fire over the wall to the standard required by the current Building Regulations guidance and which is set out in BR135. The Expert Panel’s advice is that, based on these test results, and in the absence of any other large scale test evidence, it is unlikely that any combination of ACM cladding with fire retardant polyethylene filler and rigid polymeric foam insulation would pass the BS 8414-1 test, and therefore fail to meet current Building Regulations guidance. This combination of materials therefore presents a notable fire hazard on buildings over 18m.
However, wall system with stone wool insulation passed the test, which means the wall system adequately resisted the spread of fire over the wall to the standard required by the current Building Regulations guidance and which is set out in BR135. The Expert Advisory Panel’s advice is that this result shows one way in which compliance can be achieved and offers an indication of how remedial works could be specified for those buildings that have been found to have problems. Nevertheless, it is important to note that there are many different variants of this cladding and insulation and it is possible that products from different manufacturers may behave differently in a fire.
- ACM cladding with A2 filler with PIR foam insulation and stone wool insulation (test 5 and test 6 respectively)
Wall systems with PIR foam insulation and stone wool insulation both passed the test, which means they adequately resisted the spread of fire over the wall to the standard required by the current Building Regulations guidance and which is set out in BR135. The Expert Panel’s advice is that these results shows two ways in which compliance can be achieved and offer an indication of how remedial works could be specified for those buildings that have been found to have problems.
However, the composition of different products from different manufacturers will vary and it is possible that products from different manufacturers may behave differently in a fire. Equally, it is important to note that the materials used may have been fitted or maintained differently, to how the tests were specified and constructed, which can affect the safety of the cladding system.
Additional personal conclusions
In view of the results, I would like to add a number of additional personal conclusions to those shown by the Expert Panel’s advice.
- Compliance with the requirements shown in BR 135:2013 and therefore the successful overcoming of the large-scale test BS 8414-1 depends mainly on the type of core used in the ACM (Aluminium Composite), not of the insulation material.
- When an ACM with a limited combustibility core is used, stone wool insulation and PIR insulation wall systems behave very similarly. It is therefore possible to pass the full scale test BS 8414-1 using organic insulating materials. (Test 5).
- The use of stone wool vertical and intumescent horizontal cavity barriers does not significantly influence the tests results.
- The tests results show that the system that included PIR (Test 5) had lower peak temperature in the cavity and insulation than the stone wool system (Test 6) during the test. The peak temperature at the external side were similar for both systems.
As has been reported in different English media, a thorough investigation is being carried out on everything that happened in the fire of the Grenfell Tower in order to clarify what really happened, as with the information published today, there are different aspects that it must be clarified to avoid another similar tragedy. These aspects are also fundamental: the functioning of the detection systems, the compartmentation, the effective installation of the fire barriers, if the products installed in the façades complied with the specifications contained in the project and their compliance with the current legislation as well as if the installation process was correct.