Climate crisis, carbon and combustibles

Climate crisis, carbon and combustibles

ARTICLE · By ACAN and TTF · 09 April 2020

The UK pioneered the way in building tall from timber – constructing safe, low carbon, energy and material efficient, healthy homes, but the current movement to restrict structural timber to use below 11 metres threatens a decade of innovation.

Architects, engineers, developers and clients site several reasons for their move from traditional steel and concrete buildings to hybrid or full timber construction.

Timber offers faster, cleaner, safer and quieter construction. It’s cost effective, light, creating better quality buildings and a healthier living environment. Most cited however is it’s low carbon footprint as compared to energy intensive, heavy materials like concrete and steel.

However, following the Hackitt review into the Grenfell tragedy, legislation changed. A ban on combustible materials, while welcomed on the cladding which contributed to fire spread, was broadened to include all parts of the external wall above 18 metres.

Combustible materials were banned in and on the external walls of residential buildings with a top storey above 18m. This effectively excludes 31% of residential properties in ‘100 UK CLT Projects’ book from being built in the UK in the future.

Now the Government is proposing via the Combustibles Materials review to reduce this threshold to 11m. If this proposal goes through it would exclude 56% of the residential properties in ‘100 UK CLT Projects’ being built.

The timber industry of course focuses on fire safety first, welcoming the recent Government announcements that sprinkler systems and consistent way finding signage in all new blocks of flats above 11 metres will become mandatory.

We have supported the creation of a new Building Safety Regulator, now being established in shadow form to assist with regulatory decisions made at key points during the design, construction, occupation and refurbishment stages of buildings in scope.

We continue to advocate for mandatory, comprehensive fire-risk assessments during the design process, and are keen to work with legislators on new UK scientific, research-based evidence programmes and testing regimes, like those in the USA, Canada and Australia.

However, excluding safe structural timber from the palette of structural materials that the industry can draw from to build our low carbon energy efficient homes of the future, will not guarantee safer homes, but may create an illusion that it has done so.

The Committee on Climate Change has made it clear that every industry must respond to the climate crisis. Their report on UK Housing: Fit for the future? called on the industry to increase their use of sustainable timber.

Architects and engineers are at risk of falling short against their responsibilities if they do not design and advocate for reducing the embodied carbon and energy of the fabric of all buildings being designed immediately.

Now if the current proposal goes ahead, extending the ban on combustible materials in and on external walls down to 11 metres, without creating a path for safe structural timber construction to continue, they will have lost one of their greatest tools.

Research on a parametric study is being undertaken at Bath University as part of the UK FIRES research programme by Dr Will Hawkins “Initial research has shown that medium-rise buildings (of 4 to 8 storeys) are most efficient at providing internal floor-space with minimal embodied carbon due to the efficient structural use of material.”

The Confederation of Timber Industries (CTI) and Architects Climate Action Network (ACAN) are both calling on the industry to stand together and make sure the voice for safe structural timber construction is heard. We are calling for Government to:

  1. Focus the ban on combustible cladding (as distinct from external walls). This will help provide the clarity needed for designers and specifiers to build better and safer.
  2. Take a science-based approach. Use BS8414 as the base for fire safety compliance, which was found to still be fit for purpose in the Hackitt Review.
  3. Align legislation with the Scottish approach. This will encourage a common regulatory approach throughout the UK improving clarity and safety.

You can help us by responding to the public consultation on the review of the ban on combustible materials which is currently underway, with comments being received until 23:45 on Monday 13th April.

ACAN and the TTF have provided resources to aid responses and they can be accessed at and at

What is the industry saying?

Architects Climate Action Network  ACAN

“As designers, we must first ensure safety for occupants whilst responding quickly to the climate emergency. As professionals and as individuals we must hold our government to account in both the targets they set out and our strategies for achieving them. The government must immediately and actively support the use of construction materials with low embodied carbon, not ban them. We are firmly committed to protecting the wellbeing and interests of our clients and users. We now know, however, that we also have an obligation to protect the wellbeing of the planet.”

David Hopkins, TTF

An extension of the current ban down to 11 metres now threatens to severely damage sustainable construction by beginning to impact the use of timber frames. This comes at a time when we need to build more with wood – not less – if we are to solve the housing and climate crises.”

“For industry, the core problem of the legislation is clear  – it tars the entire external wall with the same brush despite there being no evidence that structural walls pose the same fire risk as the external cladding, and no justification for treating the two in the same way.”

Anthony Thistleton & Andrew Waugh, Waugh Thistleton Architects

“The UK is a world leader in the development of engineered timber construction with over 500 buildings completed. As the government acknowledges, this change in regulations will have an impact on the continued innovation and development of low carbon construction, and hence on the rate at which the construction industry can tackle climate change”

“It is imperative that architects recognise the impact of their work on the environment. Waugh Thistleton Architects will continue to research, design and build using low carbon technologies and reducing our reliance on concrete and steel.”

Alex de Rijke, dRMM

“dRMM were the UK’s first architects for a CLT public building in 2004 – the government-funded Kingsdale School – and accordingly had to present the European material to central government, local authority and fire brigade. All were convinced then and now by the evidence that, when properly sized and detailed, CLT is not only safe in a fire, but safer than many other standard industry materials such as steel – ironically the default material for buildings over 18 metres.”

“This political knee-jerk reaction is uninformed and counter-productive. Banning safe timber construction prevents the creation of healthy and safe cities, and worsens the global environmental crisis of carbon emissions due to use of materials like concrete and steel,”

Toby Maclean, Entuitive – Consulting Engineers

“The building height at which combustible cladding or external walls are banned is not the right question.  The question is how the fire safety of all buildings be improved and the Hackitt review goes a long way toward answering that. Restrictions on combustible cladding (as distinct from external walls) should be based on building use and compartmentation and risk of the cladding compromising that compartmentation.”

”A problem with the proposed ban is that the banning of combustible external walls (as distinct from combustible cladding) does not achieve the desired objective but may create the illusion that it has done.  In order to properly manage the risk of fire spread from combustible structure (and other fire risks) then a fire safety engineering approach is required.”