- Alison Darvill, associate director, Bennetts Associates
- Nigel Ostime, partner and delivery director, Hawkins\Brown
- Jennifer Juritz, head of environmental design, David Morley Architects
- Robert Shirville, area sales manager, Rockwool
- Will Wigfield, product manager, Rockwool
- Hattie Hartman, sustainability editor, The Architects’ Journal
Fire safety and the environment are both ‘life safety issues’ that need to be reconciled in building design, according to Hawkins\Brown partner Nigel Ostime.
Ostime was speaking at a Rockwool-sponsored roundtable on fire safety and sustainability, held during last month's AJ Fire Safety Design virtual conference. Chaired by AJ sustainability editor Hattie Hartman, the session, which coincided with the 26th United Nations Climate Change conference, focused on the use of construction materials, asking: what are the top considerations for architects in balancing fire safety with net zero greenhouse gas emissions?
Ostime, co-chair of a Housing Forum working group that published the Stopping Building Failures report following the Grenfell Tower fire, said there was a need to improve both collaboration between people with knowledge of the two areas and the consistency of the targets. ‘What is net zero, for example?’ he asked. ‘We don’t really have a definition, so there’s a role for centralised regulation – but unfortunately we often only get that when we have black swan events like Grenfell, 9/11 or Lockerbie.’
There need not be conflict between fire safety and net zero emissions, he said, but pointed to the issue of using timber, particularly cross-laminated timber (CLT). ‘[Timber construction] was about to be the next big thing until 2017; then that changed and, it could be argued, we have had a rather knee-jerk reaction to it, if not in regulation then certainly in terms of what developers are prepared to build with a view to market perception,’ he says. He suggested there needed to be a more measured approach, demonstrating the performance of materials through testing – and publication of those test results. Ostime thought the issue of combustible materials was bound up with building use: his company, Hawkins\Brown, which is designing a timber railway station, has found CLT is more readily accepted in commercial and educational buildings.
Bennetts Associates is the architect behind Timber Square, a net zero carbon office campus for Landsec in London’s Bankside. The project involves two buildings: a repurposed 1950s printworks with a CLT extension, and a new 14-storey hybrid CLT and steel tower. ‘With CLT, obviously people are prone to think “Wood – fire – not good”,’ said Alison Darvill, who is leading the project for Bennetts. ‘But if you detail a steel, or a steel and concrete, or a concrete building badly, it’s going to burn anyway, so it’s about using the materials appropriately and detailing them well. CLT actually performs quite well in a fire because it chars – but it stays up.’
Darvill said using CLT took up more time on the Timber Square scheme than a standard solution because of the need to do a lot of testing and engage with the fire brigade.
Different projects use CLT and timber in different ways, and involve independent testing, and Darvill said there needed to be more sharing of that knowledge.
Jennifer Juritz, head of environmental design at David Morley Architects, said the drive for fire safety and the drive for net zero emissions had ‘compatible aspirations’. ‘The one is about immediate life safety, the other is about our long-term survival,’ she said. Both were imbued with a ‘fear of unintended consequences’. However, she said designing for fire safety and low carbon was much more challenging on retrofit projects and raised another key issue: waste. Juritz’s practice is doing refurbishment work in a number of hospitals and dealing with the question of what to strip out and throw away and what to retain.
‘It’s about striking a balance,’ she said. ‘Say, there’s perfectly good doors but the records have been lost and there’s no fire certification. Do you destructively test the doors; throw them away because that’s easier, quicker and cheaper; or do you look at ways of sensibly re-certifying projects?’
Juritz has found that decisions often boil down to what is easier to do. ‘Where fire safety is concerned at the moment it is easier for everyone just to retreat to the position of doing the safest thing, regardless of how much waste is generated,’ she said.
The government held a consultation on the use of combustible materials on the external walls of buildings last year. Proposals included lowering the height threshold for a ban on their use from 18m to 11m. The Greater London Authority announced a ban on combustible materials in external walls for homes built under its Affordable Homes Programme, regardless of height, this year.
Rockwool’s Will Wigfield noted that criticism levelled at the existing regulatory framework was that it was complicated, unclear and open to misinterpretation. Rockwool has taken a ‘binary approach’, favouring non-combustible materials. Wigfield said: ‘At this point, I’m not sure if any of us knows whether or not the existing testing regime is up to scratch.’
Robert Shirville, area sales manager at Rockwool, added: ‘I think the height limit should be taken out and a building use limit, or a building use classification, considered.’
Ostime suggested this was effectively already in place, because accommodation buildings are classed as ‘high-risk’. He said: ‘I think it wouldn’t be inappropriate to say: let’s have all buildings built with non-combustible façades. It feels more straightforward.’
Darvill said having different rules on combustible materials for different building types would make it difficult to refurbish and re-use existing buildings. ‘It needs to be something that applies to all buildings, at the same time recognising that the risk in a residential building is way higher than in a commercial building because of the level of management,’ she said.
Whatever the outcome of the government’s review, Ostime, noting that millions of people face threats to their lives due to the climate emergency, would not want to lose timber from the equation. ‘We are talking about life safety issues but it has become very apparent that the environment is a massive life safety issue, too,’ he said.