Combustible cladding on student accommodation: a search for answers

Students from both the University of Essex and South Essex College reside in the brightly coloured accommodation situated in University Square, Southend, and pictured to the right. The cladding is a ‘Trespa’ High Pressure Laminate (HPL) product, which is combustible by nature, being composed of plastic reinforced with wood fibre. One HPL product was found to have a heat of combustion (fuel energy) of 20.4 MJ/kg, nearly seven times the upper limit of 3 MJ/kg for materials of ‘limited combustibility’, as defined by Approved Document B ‘Fire Safety’.

Barring a successful large-scale BS 8414/BR 135 test and classification of the entire cladding system, including the insulation and supporting framework, such cladding can no longer be installed, under the post-Grenfell government guidance, on buildings above 18 metres. At the time of construction, however, according to information supplied in response to my enquiry to the University of Essex, who treated it as a Freedom of Information request, the Trespa panels were fully compliant with the requirements of Approved Document B Vol.2, 12.6 and Diagram 40e. Fire Retardant Trespa panels, tested and classified to national Class 0, had been specified above 18 metres. Standard panels, with an Index (I) of 19, just below the limit of 20, were employed below 18 metres. In both cases, as the Diagram shows, the requirements were satisfied.

The insulation installed behind the panels, however, was and remains another matter. Under AD B Vol.2 12.7, insulation products used in the external wall construction should be of ‘limited combustibility’, as defined in Appendix A.9 and Table A7. This Reaction to Fire class may be achieved in two main ways, through two types of fire test.

First, under BS 476 part 4 or part 11, or under EN ISO 1182, a material or product is placed in a 750 °C furnace for a period of 30 minutes (BS 476-4), up to 60 minutes (EN ISO 1182) or up to 120 minutes (BS 476-11), with measurements taken of the rise in furnace temperature, the mass loss of the specimen, and the period of any sustained flaming. Under the European classification system, for example, to achieve Class A2 and thus ‘limited combustibility’, the temperature rise must not exceed 50 °C, the mass loss must not exceed 50%, and the period of any sustained flaming must not exceed 20 seconds.

As an alternative, under EN ISO 1716, the heat of combustion (calorific value) of the product may be measured in a bomb calorimeter. A simplified version of this procedure has been employed by the BRE for its post-Grenfell tests of ACM samples. As stated earlier, the heat of combustion must not exceed 3 MJ/kg if the material is to be Euro Class A2 and of ‘limited combustibility’.

In a Freedom of Information response of 4 July 2018, the University of Essex stated that the insulation employed on the Southend building was ‘Kingspan Kooltherm insulation board’ and has since confirmed it to be Kingspan’s rainscreen product Kooltherm K15.

Like the rest of the Kooltherm range, K15 is a phenolic foam board. A typical value given for the heat of combustion of phenolic foam is 29 MJ/kg, nearly ten times higher than the limited combustibility criterion. It starts to decompose between 350 and 500 °C, and ignites between 530 and 580 °C.

That Kooltherm K15 would fail the 750 °C furnace tests is demonstrated by the actual classification of the product. In a Declaration of Performance issued in July 2013, the Reaction to Fire performance is given as Euro Class C, two grades below the minimum of A2 consonant with ‘limited combustibility’.

Indeed, Kingspan themselves, in their current Technical Bulletin on ‘Routes to Compliance: Fire Safety’, state that:

Kingspan Kooltherm® K15 Rainscreen Board cannot be classified as non–combustible or of limited combustibility, and so, the linear route to compliance is not open.

It follows that, to be compliant with Approved Document guidance, and barring a Fire Engineering analysis, which is hardly suitable for a building project of this modest scale, the entire cladding system would have had successfully to achieve a BS 8414/BR 135 classification.

Kingspan have helpfully provided information about thirteen cladding systems incorporating Kooltherm K15 that have been successfully tested and classified to BS 8414/BR 135. None of these systems used Trespa or other HPL products for the outer cladding. In addition, one system is listed that failed to achieve a successful BS 8414/BR 135 classification. This was a system with Kooltherm K15 and Trespa panels. The test was terminated, according to BS 8414 test procedures, because of flame spread above the surface of the rig after 43 minutes.

In December 2017, the government issued Advice Note 14 for owners of buildings with non-ACM cladding systems. Paragraph 11 concerned systems that incorporate materials that are not of ‘limited combustibility’. Although the specified Trespa panels met the Diagram 40e requirements, neither they nor the Kooltherm K15 insulation boards are of ‘limited combustibility’, and thus the advice contained in the paragraph would seem applicable to the Southend building. It states that in order to ‘determine whether the standards for external wall systems set out in current Building Regulations guidance would be met’, building owners should ‘determine if the external wall system has completed a BS 8414 test and successfully attained BR 135 classification’.

Accordingly, I wrote to the University of Essex on 24 May 2018 to ask whether they had followed this government advice and determined whether the cladding system employed on the Southend building had indeed been successfully tested and classified to BS 8414/BR 135. Their Health and Safety Office replied on 21 June to say that the cladding ‘meets current fire safety standards’. No reference was made to Advice Note 14, which had been the subject of my enquiry. Further enquiry was made, asking again whether the advice of paragraph 11 of the advice note had been followed, whether they would agree that the cladding is combustible, and requesting details concerning the Trespa panels and the insulation.

In their response of 4 July, the University of Essex helpfully gave full information about the products used, but declined to comment on their combustibility or on whether the advice of paragraph 11 had been followed. They pointed out instead that they had heeded the guidance of paragraph 3 to take professional advice. The advice they had received was that ‘testing is not necessary at this time’.

I asked the University of Essex further questions on 26 July about the advice they had received and for confirmation that, as the insulation was combustible, the system was therefore non-compliant with the ADB guidance. The University of Essex answered on 8 August by observing that ‘the cladding’ was compliant with Approved Document B. But ‘the cladding’, in common parlance, refers only to the outer cladding and not to the insulation!

They stated that Advice Note 14 was ‘not applicable’, because there was nothing ‘to cause concern’ about the fire safety of the cladding. They had pointed out on 4 July that the Advice Note was ‘for the attention of anyone … concerned about the fire safety implications of [non-ACM] external wall systems’. The University seems not to be concerned, and so apparently regards the Advice Note as not applying to them!

On 14 August, I asked more specifically whether the University would agree that the insulation was non-compliant with the Approved Document guidance. They replied on 29 August by saying that they did not agree that the insulation was non-compliant, since it ‘is class 0 rated throughout’. But the insulation is not required to be Class 0, which is a Reaction to Fire classification intended primarily for internal linings. It is required to be of limited combustibility.

In an endeavour to understand how the University of Essex could claim compliance with the Approved Document guidance on the basis of the insulation satisfying a requirement different to that specified in the guidance, I asked some follow-up questions on 5 September. In their reply of 25 September, the University implicitly withdrew their claim of compliance for the insulation on the basis of a Class 0 classification, and substituted an alternative claimed basis for compliance. They stated that ‘the insulation … had a successful BS 8414/BR 135 test and so is compliant with the requirements of Approved Document B, paragraph 12.5’.

But BS 8414/BR 135 is a test for ‘cladding systems’, not for individual products like insulation boards. The test referred to by the University was of a system that incorporated the same insulation product, Kooltherm K15, but a different type of cladding panel. The Classification Report makes clear that the classification applies only to the specific system tested, making it irrelevant to the University Square accommodation. Since no basis remains on which to claim compliance for the installed cladding system, it would seem incumbent upon the University of Essex to replace it with a compliant and safe façade.

***

Reply from the University of Essex, 13/05/18

***

The safety of our students is our priority and we have extensive safety measures in place at all our buildings. This includes the highest standard of fire alarm system, fully-trained security staff on-site 24-hours a day who will respond to any alarm activation within two minutes and procedures for full simultaneous evacuation if an alarm is activated.

Following the Grenfell Tower fire the University carried out a holistic review of fire safety at University Square, taking account of guidance issued by the Ministry of Housing, Communities and Local Government and we are satisfied the arrangements we have in place ensure the safety of its occupants.  At our request, Essex Fire and Rescue Service also inspected University Square and confirmed that they are satisfied with the fire safety arrangements in the building.

This article is one person’s assessment of the individual materials used and is only a partial assessment of the whole integrated system installed at this location. We think we are responding appropriately by asking an independent consultant to look at the issues raised as part of our own review of the cladding system as a whole in the light of the latest national guidance and discussions around these issues.

__________

How to cite this blog post (Harvard style) 

Chapman, A. (2018). ­Combustible cladding on student accommodation: a search for answers. Available at: https://www.law.ox.ac.uk/housing-after-grenfell/blog/2018/11/combustible-cladding-student-accommodation-search-answers (Accessed [date]).