Green wall systems marketed with questionable fire safety claims

Architects in the UK may be under false impressions about the fire-safety of green walls due to non-standardised test procedures – including being soaked with water before testing – that are not clearly mentioned in marketing materials, a Dezeen investigation has found.

The UK's industry-leading green wall system was fire tested when it was so wet that 45 per cent of its total mass was water, according to documents seen by Dezeen.

Another major supplier markets its green wall system as having good enough fire performance to be used on high-rise residential buildings, based on testing carried out without any plants in place.

Concerns over green walls' potential to spread fire

"I am increasingly concerned about the way certain living wall systems are marketed in the UK without the necessary certification to support their claims," one architectural designer who specialises in facade design told Dezeen.

"This is dangerous. I am particularly alarmed by the influence major green wall system suppliers wield – not only as perceived experts in planting but also as self-appointed authorities on fire safety and regulation."

Green walls are sometimes added to building facades by architects seeking to introduce nature into an urban environment, with benefits for biodiversity, air purity and temperature regulation.

They have become increasingly common as concerns about the built environment's ecological impact have grown.

But fire experts and insurers have previously raised concerns about their potential to spread a blaze from floor-to-floor, either via burning plants or ignition of the plastic components in which they are sometimes potted.

Testing under "ad hoc" conditions

Viritopia, formerly known as ANS Global, has supplied green and living wall systems for dozens of building projects around the UK, from hotels to data centres and high-rise offices.

In continuing professional development (CPD) sessions and marketing brochures given to architects, seen by Dezeen, the company claims its product has a Class B s2-d0 grade for fire.

This, it says, is the highest classification a green wall can obtain and allows specifiers to "design and integrate living walls into nearly all buildings apart from residential buildings over 11 metres in height".

However, a classification report from the testing agency Warringtonfire, produced in September 2021, reveals that the system was tested in "ad hoc" conditions, which means that it that did not meet the normal testing standards prescribed by the UK Accreditation Service.

As a result, the report said the classification "should be treated with caution".

A further fire-engineering assessment, produced by International Fire Consultants in February 2020, shows that 3.5 litres of water were added to every planting module before the fire test was carried out – meaning the mass of the tested system was 45 per cent water.

However, in marketing materials and CPD presentations potential clients are offered the Class B grading at face value.

They are not told that the testing was "ad hoc" and to be "treated with caution", or that it only applies if 45 per cent water content is maintained.

A page on Viritopia's own website promising "all you need to know" about the fire safety of its systems advises clients that keeping the system well watered is "vital", but does not mention that its fire safety classification would not apply if water supply was disrupted, or that the testing was ad hoc and to be treated with caution.

"Because this is a live product, it's impossible to test it in the same way as non-organic claddings so UKAS accreditation isn't viable," said Viritopia managing director Richard Silcock in response to Dezeen's findings.

"Instead, all living wall providers must meet a bespoke set of testing criteria, referred to in the fire safety industry as 'ad hoc' testing."

"This testing was produced with government guidance and in collaboration with leading living wall specialists. It's a rigorous testing process but ad hoc tests will always carry the industry norm caveat 'treat with caution'."

He added that Viritopia's green walls are sold with automatic irrigation technology that maintains the required level of water saturation, with alarms to alert engineers of any changes in water distribution.

"The testing is undertaken with soil saturated to around 45 per cent because that is the level that the wall will always be maintained at. It's the real-world testing scenario," he said.

"Safety is our priority. We have, and will always, support the development of the highest safety standards possible."

The company also pointed to one CPD presentation where it openly tells clients that "without maintaining the level of water application used in the testing conditions, the living wall would not meet the standards". Other materials omit this warning.

"Just not what the test was meant for"

The Class B testing regime is designed for conventional building facade systems.

Its normal rules include a requirement for materials to be kept in a dry environment for 28 days at a temperature of between 23 and 25 degrees Celsius and 50 per cent humidity prior to testing – conditions that are impossible to maintain with live plants.

As a result, some test houses provide green-wall manufacturers with adapted tests – such as that used by Viritopia – that give an indicative result, despite not meeting the full requirements.

But Jim Glockling, a leading fire engineer who has helped prepare guidance on green and living walls for the insurance industry and other professional bodies, expressed concerns about the usefulness of the adapted tests.

"The test is meant for flat materials that do not change with time," he told Dezeen. "Over time, the plants change and different ones grow at different rates from the others. So, basically, everything changes. It's just not what the test was meant for."

Glockling suggested that a better approach would be to safety test green walls in poor condition.

"The test could be useful if the plants were dried out to a credible worst-case condition of irrigation, specific pass/fail criterion was developed and the structure was entirely non-combustible," he said.

"I mean, there's no other testing that you're allowed to do on products where you are essentially allowed to put a wet flannel over it prior to testing."

Manufacturer "reviewing" its website following Dezeen findings

Marketing materials for another green-wall supplier, Dutch company Sempergreen, also appear to make claims that do not match up with its testing.

In February 2021, Sempergreen claimed to have obtained an A2 fire safety grading for its system, which it said made it a "a fire-safe solution for high-rise projects" or "other projects with very strict fire safety requirements".

But the relevant testing certificates, seen by Dezeen, show that Sempergreen had tested the glass-fibre and mineral wool potting system only – not the plants that would be installed on a real building.

A spokesperson for the company said it was "reviewing the wording" on its website after being contacted by Dezeen.

"The A2 classification we refer to was awarded based on independent testing of the structural components of our Flexipanel, specifically the mineral wool and glass fibre fabric," the spokesperson added.

"This test did not include vegetation, which is also clearly stated on the certificate. We aim to communicate our claims as clearly and accurately as possible."

"While we provide guidance and information to architects and project developers, we never take the place of independent fire-safety consultants."

Suppliers educating industry "bears striking similarities" to Grenfell

One architectural designer expressed alarm about green wall manufacturers positioning themselves as educators on fire safety.

"They have taken a leading role in shaping industry understanding of fire regulations, which raises serious concerns," he said. "This situation bears striking similarities to the influence that major rigid board insulation suppliers exerted before the Grenfell disaster – an issue that was rightly exposed during the inquiry."

Grenfell Tower was a social-housing tower block in London that was destroyed in a fire in June 2017, killing 72 people, after flames spread rapidly across its cladding system.

The public inquiry into the causes of the disaster particularly highlighted a lack of understanding among those involved in the cladding project about the risks of the materials being used.

It was revealed that Celotex, the firm that sold most of the insulation used on the tower, had offered CPD sessions to architects, including the studio appointed to the Grenfell project, that did not make clear the product was combustible and unsuitable for high rises.

Another manufacturer, Kingspan, had put pressure on building-control bodies to accept its insulation in tall buildings, despite it not meeting the basic requirements of official guidance.

While neither company's product was found to be the major cause of the spread Grenfell fire, their behaviour was sharply criticised in the report.

The photos are stock images via Shutterstock.

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