3. Part 2 – Definition and Ban of Category 3 Metal Composite Material (MCM)
3.1.1 Given concerns about the use of the highest risk cladding materials and interpretation of data from large-scale fire test results in new developments, changes were made to Section 2 (fire) of the Technical Handbook in April 2021. As stated in paragraph 1.1.3, these changes include the need to avoid using category 3 MCM cladding in new building work and the removal of reference to BS 8414 as alternative guidance.
3.1.2 The expert review panel considered a number of options relating to the definition of category MCM. One option was to lower the threshold of calorific value of cladding material from 35 to 20 MJ/kg. However, widening the scope to all cladding material with a calorific value of 20 MJ/kg was not considered a practical solution.
3.1.3 The expert panel agreed the definition should be close to that used by the Ministry of Housing, Communities and Local Government (MHCLG) as part of the aluminium composite material (ACM) panel screening test programme following the Grenfell Tower fire i.e. ACM (category 3) with a core material having a calorific value > 35 MJ/kg.
3.1.4 Thin MCM cladding panels are non-homogeneous products made from generally, aluminium, zinc or copper sheets around 0.5 mm thick bonded together with a variety of core materials with a range of calorific values. Question 2.1 of the consultation sought to establish if respondents agreed with the proposed definition of MCM category 3 which is shown below:
"Any panel or sheet, having a thickness of no more than 10mm, which is comprised of a number of layers, two or more of which are made of metal, alloy or metal compound and one or more substantial layer of which is made of a material having a gross calorific value of more than 35 MJ/kg when tested in accordance with BS EN ISO 1716:2018 entitled "Reaction to fire tests for products – Determination of the gross heat of combustion (calorific value)" published by the British standards institution in 2018 and for these purposes a substantial layer is one which is at least 1mm thick or has a mass per unit area of at least 1kg per m²".
3.1.5 Market research has indicated that there are currently no MCM products on the market with an overall thickness of more than 7mm. However, markets can fluctuate and it is therefore important to decide for futureproofing if the ban on MCM should be within regulation (which is less practical to amend and requires parliamentary time) or be within guidance (which can be amended much quicker).
3.1.6 Question 2.2 sought to establish if the ban on MCM category 3 should be in guidance or regulation.
3.2 Question 2.1 -Do you agree with the definition for MCM (category 3)?
3.2.1 Question 2.1 asked respondents if they agreed with the definition for MCM (category 3) (see para 3.1.4 above) with Table 3 below providing the results. No one response category achieved a majority, but 48% of respondents 'strongly agreed' or 'agreed' with the definition. While only 17% of respondents 'disagreed' or 'strongly disagreed' with the definition, some 36% or responses were neutral.
3.2.2 A majority of respondents in the construction industry, local authority and other sectors supported (agreed or strongly agreed) the proposed definition. The majority of individuals and trade associations were neutral on the definition with all research establishments/fire test houses disagreeing with the proposal.
|Strongly Agree||Agree||Neither Agree or Disagree||Dis-Agree||Strongly Dis-Agree||Not Answered||Total|
|Research Estab./Fire Test House||-||-||-||1||1||-||2|
|% answering question||12||36||36||10||7||100|
Note: percentages may not sum due to rounding
3.2.3 There were 49 comments made in response to this question. Responses are considered separately for those agreeing and those disagreeing with the quantitative part of the question.
Agreeing with the Proposed Definition
3.2.4 Several respondents stated that the proposed definition was reasonable and described such materials clearly without ambiguity. The performance benchmark was also welcomed as a way to restrict the use of the highest risk cladding products.
Specific Details related to Thickness and Calorific Value
3.2.5 Several respondents also made very specific comments on the proposed definition, particularly in relation to thickness and calorific value:
- Thickness: a few respondents questioned the upper limit of 10mm and suggested that this left the definition open to misuse and may permit systems of greater thickness to avoid the exclusions. One respondent recognised that the proposed thickness reflects current practice and may require review in the future while another felt that it will "future proof" other products which may be manufactured over 7mm thick.
- Calorific Value: One respondent felt that reducing the calorific value to around 20 MJ/kg would significantly limit the availability of suitable products and inadvertently restrict use of many A2 rated products. Another felt that while there could be benefits in further reducing the calorific value, the technical standards provide sufficient guidance to ensure that any unsafe material would not be permitted as part of any external wall system. One further respondent felt that the details relating to calorific value could be difficult to interpret without expert input from a fire engineer and may leave them reliant on the manufacturer's technical information and guidance.
3.2.6 A few respondents referred to similar definitions being discussed in England and it was suggested that it would be better to have agreement across the UK in order to facilitate the market.
3.2.7 One respondent felt the wording could be better and suggested
"…which comprises two layers of metal, alloy or metal compound, between which is located a substantial layer of material having…"
Disagreeing with the Proposed Definition
Specific Details related to Thickness and Calorific Value
3.2.8 Several respondents made very specific comments on the definition in relation to thickness and calorific value:
- Thickness: the rationale behind the decision to restrict or prohibit the use of thinner category 3 MCM panels was questioned as thicker panels may provide a higher fire load. It was suggested that "having a thickness of no more than 10mm" is deleted from the definition. One respondent also suggested that cladding product of any thickness should be limited by calorific value in MJ/kg, using established test and classification standards. They also stated that the requirement should apply to any homogenous material or composite product, regardless of the thickness of the composite.
- Calorific Value: lowering of the calorific value to at least 20 MJ/kg was supported by a few respondents. One respondent suggested that calorific value should be limited on the basis of unit area of cladding (to 35 MJ/m2) as opposed to bulk material mass as this was felt to be more representative of the actual fire load/risk involved and obviates the need to define "substantial layer". It was also suggested that the choice of 35 MJ/kg as the limit for the gross calorific value for substantial layers of MCM panels is arbitrary and further analysis is required to determine the most relevant limit.
3.2.9 Related to the issues of thickness and calorific value, the issue of testing was raised by a few respondents. One respondent suggested that "cladding product of any thickness should be limited by calorific value in MJ/kg, using established test and classification standards" while another suggested that whether a product is 'fit for purpose' should be based on clear and unambiguous test certification, not a prescriptive ban. It was suggested that the threshold is "Cladding and Insulation product of Class A2-s1,d0 to BS EN 13501-1 at all heights and for all building use categories". It was suggested that this threshold would encourage market innovation while recognising that some Class A1 and Class A2-s1,d0 MCM products are already on the market.
Definition too Restrictive
3.2.10 Several respondents felt that the definition was too limiting and allowed for loopholes to circumnavigate the requirements. For example, a new MCM product that was 10.1mm thick and having a substantial layer with a gross calorific value of more than 35 MJ/kg would not be covered by the definition as would a product which used something other than metal to form one of the faces of the product. One respondent suggested that a definition for a category 1, 2, or 3 should be given which would apply to current and future products.
3.2.11 A few respondents also felt that the definition was too restrictive in terms of the product that it was applied to. One respondent suggested that there are other products on the market that may have a similar calorific value and rapid flame spread (e.g. honeycomb aluminium panels encased in fibreglass coated adhesive) while another felt that "if it is the opinion of the panel that external surface products with a substantial layer with a gross calorific value of more than 35 MJ/kg pose a risk to the relevant person then it is recommended that this applies to any products and not just MCM panels".
3.2.12 One respondent also highlighted that there is much confusion about metal composite panels and insulated panels, with the latter capable of meeting large scale system tests such as BS 8414. It was suggested that the main concern should be the polyethylene content and not the metal composite panels which, with the correct filler, can achieve an A2 rating.
Neutral Responses regarding the Proposed Definition
3.2.13 The issues raised by respondents neither agreeing or disagreeing with the proposal had also been raised by other respondents to the question. For example:
- Several respondents suggested that reference to the maximum overall thickness of the panel should be removed to prevent confusion and avoid potential abuse.
- Several respondents suggested that the definition was consistent with the wider industry understanding of a MCM category 3 material. However, respondents questioned whether the definition would apply to other products with a polyethylene core between two non-metallic facings.
- It was suggested that the research behind the lower limits on thickness and mass had not been referenced but it was "assumed that at less than 1kg/m2 (less than 35 MJ/m2 ) the science has shown that fire spread cannot be self fuelling".
3.3 Part 2 Question 2.2 – Do you think that the ban on MCM (category 3) materials should be in guidance or regulation?
3.3.1 Question 2.2 asked respondents if they thought that the ban on MCM (category 3) materials should be in guidance or regulation with Table 4 below providing the results. The majority (60%) of respondents felt that the ban should be in regulation with 22% of respondents supporting the ban being in guidance.
3.3.2 Respondents in the consultancy, individual and other categories clearly supported the ban being in regulation. The majority of local authority respondents supported the ban being in guidance with the other categories being more evenly spread across regulation, guidance and unsure.
|Guidance||Regulation||Not Sure||Not Answered||Total|
|Research Estab./Fire Test House||-||1||1||-||2|
|% answering question||22||60||18||100|
3.3.3 There were 54 comments made in response to this question. Responses are considered separately for those supporting the ban being in regulation, guidance and those who were unsure.
Ban in Regulation
3.3.4 Of the respondents supporting the ban being included in regulation, there were many comments on the following two main themes:
- Stronger statement: many respondents felt that if a product is to be banned it must be in regulation. Regulation is much stronger than guidance, it is unambiguous and it provides a clear legal requirement that can be enforced.
- Discourage alternative solutions: many respondents also felt that if the ban was not in regulation, it would be open to interpretation and allow alternative approaches to justify the use of combustible products in external wall construction.
3.3.5 The following quotes provide a flavour of the comments on these two themes:
"By banning MCM (category 3) materials in regulation, the Scottish Government would provide the clarity needed on this issue to raise standards in the built environment".
"The only way that we can see that ensures a ban is effective is through regulation. Guidance will not send the same message over their use and therefore runs the risk of sending the wrong message when the intent is a ban of this specific type of material".
"We cannot allow another situation like Grenfell and it would be better if MCM was banned. It should be written into legislation and there will be no confusion by anyone as to what can be installed on buildings over 11m in height".
"Regulation could prevent or restrict any alternative engineered solutions being proposed for different building types".
3.3.6 A few respondents highlighted that it is only regulation that will achieve compliance and that there is a need to back-up the regulation with clear and unambiguous guidance.
Ban in Guidance
3.3.7 Of the respondents supporting the ban being included in guidance, there were several comments on two main themes:
- Speed: several respondents suggested that having the ban in guidance would be quicker to implement and change if necessary.
- Flexibility: several respondents felt that guidance would offer enough flexibility to change to a variety of situations and new innovative products.
3.3.8 The following quotes provide a flavour of the comments on these two themes:
"We believe that adopting a regulatory ban makes it much more challenging and time consuming to seek amendments, which is of particular concern should the Scottish Government choose to remove citation of BS 8414 and BR135 pending its formal review process"
"..any proposed revisions to definition (if necessary) could be updated in a more efficient manner"
"The definition should be placed within the guidance section of the standards to allow quicker reaction to any future changes in products, manufacturing, research findings or other incidents".
"..the limits and description need to be easily changed as new information and new products become available. This will be better facilitated through guidance than regulation. It will also mean that it is possible to negotiate around unintended and unreasonable consequences should they arise".
"A regulatory ban provides no alternative routes to compliance and, as has been seen the following the ban of combustible materials in the external walls of buildings in England, has the potential to cause unintended consequences and hardship for homeowners who find themselves in a building containing a banned cladding material".
3.3.9 A few respondents also raised the issue of performance-based standards. One respondent felt that "the preferred route to exclude any construction product is via minimum performance criteria (based on large scale system testing performance) and provided by guidance within the Technical Handbooks rather than as a prescriptive ban at the product level which may have definitional issues".
Unsure of whether the Ban should be in Regulation or Guidance
3.3.10 For those respondents who answered "unsure" to the question, the comments were focused on three themes:
- Disagree with ban: a few respondents felt that the question was biased as there was no option to say that a ban is not considered the appropriate course of action.
- Definition: a few respondents questioned the definition and felt it should be expanded to ensure a clear understanding of which materials are included and excluded. It was suggested that it should be applicable to all materials/products that fall into a defined category with a defined unacceptable performance level.
- Prescriptive ban: a few respondents did not support a prescriptive ban believing that the restriction to use of any material should be enforced through the application of the mandatory standards and the guidance within the Technical Handbooks as an extension of system performance rather than as a prescriptive ban.
3.3.11 The following quotes illustrate some of these themes:
"If a ban was to be considered, it should be applicable to all materials and/or products that fall out with a clearly defined performance category which is considered acceptable. This approach of defining an acceptable performance criteria would cover future materials and/or products and not just existing ones".
"The need for products to meet the functional criteria and guidance in the Technical Handbooks should be maintained so that any product can prove its integrity as part of a system through large-scale testing"
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