Last edited 08 May 2024

Celotex RS5000 PIR insulation

A rainscreen (sometimes referred to as a ‘drained and ventilated’ or ‘pressure-equalised’ façade) is the outer part of a double-wall construction that can be used to form the exterior walls of buildings. Typically, rainscreens are formed of relatively thin, pre-fabricated panels that prevent significant amounts of water from penetrating into the wall construction. Thermal insulation, airtightness and structural stability are provided by the second, inner part of the wall construction.

Celotex RS5000 is a type of thermal insulation designed specifically for use in rainscreen cladding systems. It forms a layer of thermal insulation between the rainscreen cladding and the inner part of the wall construction. It is formed from a rigid polyisocyanurate foam core (PIR) and has a low-emissivity textured aluminium foil facing.

Celotex have confirmed that they supplied this insulation for the Grenfell Tower refurbishment.

On 14 June 2017, a fire broke out in Grenfell Tower, a block of flats in North Kensington, London. The fire spread up the outside of the Tower unexpectedly quickly, and initially, suspicion focussed on the Reynobond PE ACM cladding rainscreen panels. However, on 23 June 2017, the Police confirmed that small-scale fire tests had been carried out on the Reynobond ACM cladding and the Celotex insulation and both had failed.

Detective Superintendent Fiona McCormack said; "The insulation was more flammable than the cladding. Tests show the insulation samples combusted soon after the test started."

The Building Regulations require that materials used in buildings with storeys more than 18 m above the ground have limited combustibility. Limited combustibility can be demonstrated by testing materials in accordance with BS 8414 and satisfying the performance requirements set out in BR 135.

The Celotex website states specifically that Celotex RS5000; “Has been tested to BS 8414-2:2005, meets the requirements in BR 135 and (sic) the first PIR insulation suitable for rainscreen cladding applications above 18 metres in height” Ref Accessed 23 June 2017.

The product is advertised as having a Class O fire performance and is intended for use in warm steel frame constructions (that is the insulation is on the outside of the construction) for ventilated facade applications (rainscreens).

BR 135, 'Fire performance of external thermal insulation for walls of multistorey buildings', sets out principles, design methodologies and fire spread performance characteristics for non-loadbearing cladding systems. It was first published in 1988 in response to the increasing use of thermal insulation in the refurbishment of multistorey buildings.

BS 8414-2:2005, 'Fire performance of external cladding systems', describes the test method for non-loadbearing external cladding systems.

'Rainscreen Cladding Compliance Guide when specifying Celotex RS5000 in buildings above 18 metres', explains the route taken to meet the performance criteria set out in BR 135 through testing to BS 8414-1:2002 or BS 8414-2:2005.

This process involves testing the insulation system as a whole, not just the insulation material itself. It states:

Fire stopping was provided by ventilated horizontal fire breaks positioned at each floor slab edge and above the hearth opening. Vertical non-ventilated fire breaks were provided at the edges of both the main face and the return wing and around the hearth opening. Ventilated fire barriers comprised of stonewool insulation with Class O aluminium foil facings and a continuous bonded intumescent strip. Non-ventilated fire barriers comprised of stonewool insulation with Class O aluminium foil facings specifically intended to fully fill the void.

It makes clear that the fire performance and classification reported only relate to the components and construction described. Any changes would need to be considered by individual building designers.

It was also reported by the press that PIR insulation can emit hydrogen cyanide in the event of a fire, and that this could have contributed to some of the injuries seen in the victims of the fire. Richard Hull, professor of chemistry and fire science at the University of Central Lancashire said; "...every flat would have its own source of PIR foam, which would have produced enough hydrogen cyanide to kill all the people in that flat,"

The health and safety datasheet associated with the product notes; 'The products will burn if exposed to a fire of sufficient heat and intensity. As with all organic materials, toxic gases will be released with combustion. Do not incinerate waste. Do not inhale fumes. Fire fighters should attack the fire according to the combustible materials present, and use breathing apparatus.' Ref

It was later reported by the BBC on 12 July 2017, that medical discharge papers revealed 12-year-old Luana Gomes had been treated for the effects of cyanide poisoning, and that her sister and mother had also been treated. Ref

Following the findings of the Police tests, Celotex issued a statement on 23 June 2017 saying:

... Celotex believes that the right thing to do is to stop the supply of Celotex RS5000 for rainscreen cladding systems in buildings over 18m tall with immediate effect (including in respect of ongoing projects), pending further clarity. "... Given the developments of the past twenty four hours, we wish to discuss with the authorities how we can restore confidence in the products that we supply to the above 18m market.

On 26 June 2017, Sajid Javid announced the creation of the Grenfell Tower independent expert advisory panel to advise the government on the fire.

On 29 June 2017, Theresa May announced that Sir Martin Moore-Bick had been appointed to lead a Public Inquiry into the fire. For more information see: Grenfell Tower Inquiry.

On 6 July 2017, the Grenfell Tower independent expert advisory panel advised that further testing should be carried out by BRE to establish how different types of ACM cladding behave in a fire in combination with different types of insulation. This, they suggest will help landlords decide what further measures may be needed to make their buildings safe.

The tests will look at 6 combinations of 3 different types of ACM cladding, with polyethylene, fire retardant polyethylene, and non-combustible mineral cores, combined with insulation of rigid polyisocyanurate foam and non-combustible mineral wool. The tests will be carried out in accordance with BS 8414, and involve building complete cladding systems 9 metres tall and then subjecting them to a severe fire. The results will be made publically available, but landlords should take professional advice on the implications for their buildings.


The first results of these tests were revealed on 28 July 2017, when DCMS announced that a system comprising ACM cladding with polyethylene filler (Category 3) and foam insulation, with fire breaks and cavity barriers in place did not satisfy the requirements of the building regulations. 82 buildings are thought to have this combination of materials in their wall construction. Ref

Following these results, the government issued further advice for landlords of affected buildings. Ref

Communities Secretary The Rt Hon Sajid Javid MP also announced an independent review of the building regulations and fire safety. See: Independent review of the building regulations and fire safety for more information.

On 2 August 2017, the government announced that the second series of tests had been completed, testing a system consisting of ACM cladding with a polyethylene filler (category 3) with stone wool insulation. The Grenfell Tower independent expert advisory panel advised that the combination does not meet current building regulation guidance. There are 111 buildings known to use this system. Ref

On 8 August, results of the third series of tests was published, consisting of ACM cladding with a fire retardant polyethylene filler (category 2 in screening tests) with PIR foam insulation. Again, the Grenfell Tower independent expert advisory panel advised that the combination of materials does not meet current Building Regulations guidance. It was also reported that to further build the evidence available, the government has commissioned a seventh large scale test on ACM cladding with fire retardant polyethylene filler (category 2 in screening tests) with phenolic foam insulation. Ref

On 11 August, the results of the fourth round of tests was published, relating to ACM cladding with a fire resistant polyethylene filler (category 2 in screening tests) and stone wool insulation (a form of mineral wool). The combination of materials passed the test and so can be compliant with the Building Regulations. Following the tests, Advice for building owners: large-scale wall system test 4 was published by the Grenfell Tower independent expert advisory panel.

On 14 August, the results of the fifth test, assessing ACM cladding with a limited combustibility filler (category 1 in screening tests) with PIR foam insulation were published. The Grenfell Tower independent expert advisory panel reported that these results show the combination of materials can comply with the building regulations. Ref

On 21 August 2017, the results of the sixth large scale tests were published, revealing that a system consisting of ACM cladding with a fire retardant polyethylene filler (category 2 in screening tests) with phenolic foam insulation did not satisfy the Building Regulations. Ref

On 25 August, the results of the final test were published, a system consisting of ACM cladding with a limited combustibility filler (category 1 in screening tests) with stone wool insulation. The Grenfell Tower independent expert advisory panel reported that this combination of materials can be compliant with the building regulations when installed and maintained properly. Ref

For more information see: ACM cladding testing by BRE.

In February 2018, BRE issued a statement revealing that the original tests they had carried out on the cladding system in 2014 were carried out on a test system that was not constructed according to Celotex’s design specification. The statement said; "The cladding system in that test included Celotex RS5000 and fibre cement board rainscreen (declared reaction to fire classification A2) – this was not an Aluminium Composite Material (ACM), nor was it the cladding system on Grenfell Tower." BRE made clear that they did not design, select or install the test system, and were not involved in the sample selection process. Ref

In June 2018, Housing Secretary James Brokenshire launched a consultation on banning the use of combustible materials in the external walls of high-rise residential buildings.

In August 2022 BRE withdrew it certification from all Kingspan related products.

In September 2023 BRE published an update on its decision to withdraw certification from Kingspan in August of 2022. For further information see the article; LPCB certification and Kingspan

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