Fire safety and the sustainability agenda
Where are the blind spots?
The fire safety challenges of green buildings and sustainable living were analysed at the opening session of the Green Fire Safety Issues conference, held alongside FIREX.
In his keynote presentation, Guillermo Rein, Professor of Fire Science at Imperial College London, outlined the key layers of fire protection. They are, he explained: precaution; detection, compartmentation; suppression; evacuation; and structural resistance.
None of them is perfect, he said, but hopefully enough will work together to prevent a disaster.
In the US, more reliance is placed on suppression in the form of sprinklers, whereas in the UK there is greater reliance on compartmentation.
But regulation is not the be all and end all of fire safety. The Titanic complied with all codes; lawyers can make any device legal, but only engineers can make it safe.
“So regulations are only the bare minimum and there is plenty of room above them to provide safety.”
Rein asked delegates to imagine a world in which there were no regulations but instead there was a market for safe living.
Following this logic, in terms of fire safety, the best building in terms of fire suppression would be an igloo, the best in terms of fire resistance would be a wartime bunker, and the best in terms of fire prevention would be the International Space Station, because of its strict restrictions on flammable materials.
But who would want to live in any of these?
There is an apparent contradiction in fire safety with two opposing narratives.
Looking at the exponential rise in worldwide flammable plastic production, Narrative A suggests that the end of the world is nigh.
But looking at the continuous fall in the number of fires per dwelling in London over the last decade or so, it could be said that ‘we are doing just fine’ and there’s no need to change anything.
The truth is, neither is wholly true – there are blind spots among all the stats. For example, the Grenfell Tower fire in 2017 is an outlier in the otherwise declining trend of fatalities in fires in London.
The subject of façade fires worldwide went from being a blind spot in the 1990s to being an elephant in the room.
So, where are the other blind spots?
The built environment is always changing, and fire safety must keep up. There are novel materials and features appearing before they are really understood.
But fires from these materials are not seen in the stats yet, so are not covered in regulations and standards.
Therefore, solutions to these problems are not part of our toolbox – yet.
Rein set out two examples of contemporary sustainability trends affecting fire safety.
The use of timber in construction. While reducing carbon emissions compared to steel and concrete, this still means using a product that is flammable to some degree, so fire engineering is a prerequisite to the safe design of tall buildings using timber.
Meanwhile, in terms of energy and fire, lithium-ion batteries were until recently an elephant in the room, but now statistics are being collated from the likes of London Fire Brigade to show the exponential rise in battery fires.
“My current elephant in the room is stationary energy storage systems, which are usually hidden away in basements of buildings.
“We are doing well, but we can do better. Fire engineering must keep up with building innovation in green buildings and sustainability.”
In Part 2 of the chapter, we focus in on ‘living walls’.
Designed to improve air quality and public wellbeing, Professor Ed Galea, Fire Safety Engineering Group Director at the University of Greenwich, says that the current guidance is inconsistent and not fit for purpose.
To define living walls – also known as green walls or vertical gardens – these are structures covered in living plants that can be installed onto building walls.
Speaking at the conference held alongside FIREX, Galea said that although external living walls undoubtedly provide improved public health and wellbeing, and introduce biodiversity to our cities, their fire safety implications mustn’t be ignored.
He set out examples of living wall fires, which include:
A beer garden in Sydney in 2012 where a living wall caught fire in a semi-enclosed beer garden. When a customer used a candle to light a cigarette and one of the ferns caught fire, resulting in fire spread across the wall in a few seconds
The Mandarin Oriental hotel in London in 2018, believed to have been caused by a by-product of arc welding landing on the felt lining of the planting façade
A block of flats in Ealing, West London in 2018, which destroyed a living wall and decking on the 7th floor and entered the building, damaging parts of the 7th and 8th floor corridors.
However, Galea said reports of living wall fires are relatively rare.
It’s not clear whether this is because of the limited number of living walls around the world, the incidence of fires in living walls being rare, or the under-reporting of living wall fires because they are not treated as significant.
The risk factors of living wall components include:
Individual materials such as plants, growth media, plastics for modules, backing layers and wood – all of which are combustible
The spatial arrangements of materials, including gaps and air pockets in the system itself and supporting structures
Façade designs, where, for example, the living wall abuts windows or wall penetrations and fire can spread from within to the living wall, and from the living wall to the interior of the building
The design of the system – such as the design of the irrigation network – can affect fire spread
A lack of maintenance leading to dry matter increasing flammability and fire spread risk
Environmental factors such as wind and climate change
The main regulatory guidance for England on reaction to fire performance of external surfaces of walls is contained in Table 12.1 of Approved Document B (2022), where wall materials are classified in terms of reaction to fire in accordance with BS EN 13501-1:2018, the standard for reaction to fire classification of construction products.
There’s also the test for fire performance of external cladding systems, BS 8414-1, but that’s not recommended for living walls.
Best practice guidance for living walls can be found in a 2013 guidance document, Fire Performance of Green Roofs and Walls, published by the Department for Communities and Local Government.
The guidance states that living walls must comply with the requirements of Diagram 40 of Approved Document B 2013, and yet the materials must be of limited combustibility.
These requirements are contradictory and were so even in 2013, said Galea.
Diagram 40 suggests Class B or better, whereas page 27 of Fire Performance of Green Roofs and Walls refers to “limited combustibility” i.e. Class A2 or better.
Another issue is applying living walls to the current SBI (single burning item test under EN 13823) testing regime. Problems with SBI testing of living walls include:
The small heat source of 30kw
Small specimen size – the standard SBI test requires that specimen surfaces are flat or regularly corrugated, with a thickness of no more than 0.2m
Consistency of samples of living wall – the test sample may not be representative of the original, as plants are usually trimmed to fit the test facility
Moisture levels, as SBI testing requires certain temperature and humidity parameters
Galea said it’s also possible to ‘game’ the system by, for example, saturating the living wall before a sample is tested.
“I would argue that you cannot give a Euro classification to a living thing. The alternative is a BS 8414 test which consists of a larger fire, a larger sample, and a test of the whole system.”
Galea summarised his presentation, saying:
The fire guidance for living walls in the UK published in 2013 is outdated, inappropriate and confusing
The current reaction to fire testing methodology using the SBI test for wet living wall systems is inappropriate
CFD modelling has the potential to be more cost-effective than BS8414 testing but is challenging, given the complexity of living wall systems
He therefore recommended:
The urgent update of the 2013 best practice guidance. Until the guidance document is updated, it should be removed from Approved Document B
A modified BS 8414 test could be introduced for living walls
To reduce the costs of BS 8414 testing, a pre-testing of living wall samples using CFD fire modelling, or a modified SBI test (with dry growth medium excluding plants and irrigation) to identify products likely to pass BS 8414 testing
Regular maintenance must be considered an essential component for compliance with fire safety requirements.
See Professor Galea’s full presentation here.
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