Write up - by Kate de Selincourt

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This year’s ASBP healthy buildings conference took a very wide-ranging look at the health implications of construction. The focus ranged from the invisible molecules that might enter our lungs when we are inside a building, right out to the ecological health of the far-away environments where building components originate – and where they might end up at the end of a building’s life.

Part 1: what goes into buildings, what comes out of them

Healthy building interiors and the toxins that threaten them are unsurprisingly a regular theme in the work of the ASBP. This year’s conference enabled delegates to update themselves with the latest understanding and knowledge.

Sani Dimitroulopoulou, Public Health Scientist at the UK Health Security Agency, knows an enormous amount about indoor air pollution. She was part of  an international team of colleagues that investigated the volatile organic compounds (VOCs)  most commonly reported in indoor environments in Europe. Many are known to pose a threat to health.

The team identified a total  65 VOCs that had been detected and reported in residential spaces.

The compounds have  numerous known sources, including furnishings and consumer products, cleaning materials and toiletries. But a striking proportion – 80% – are also  associated  with construction products such as glues, flooring materials, and wood products like MDF and particleboard. Some even arise from solid wood.

Sani and her co-authors found that a number of the VOCs commonly associated with building materials may also  pose particular health risks to occupants. One of the most prevalent of these, formaldehyde, is a known carcinogen, as well as a respiratory irritant implicated in lung disease such as asthma.

 Other VOCs ‘of concern’ that have been associated with building materials or components  include chlorinated organic compounds, alkanes and aldehydes, all of which are irritant, carcinogenic and/or neurotoxic.

Sani added that UKHSA are also concerned about the toxicity of ‘semi-volatile’ organic compounds such as phthalates, present in many plastics: “We really need to know more about these”.

Because formaldehyde is so ubiquitous, the UK Health Security Agency has looked at this substance particularly closely.

While it appears that indoor formaldehyde levels are declining in a little in Europe, sadly, from the little data available, this does not seem to be happening in the UK. The team at UKHSA  looked at the data to estimate the health impacts of  formaldehyde exposure among children in England. As Sani told the conference: “perhaps 4000 new patients each year” develop asthma associated with exposure to formaldehyde in the indoor air in homes.

It is not just at home children are exposed to formaldehyde – they are also at risk at school. Construction, refurbishment and refitting, cleaning, and many other activities involve the release of multiple VOCs into the indoor air.

The UKHSA is contributing to the 2024 CIBSE TM57 guidance on integrated school design. The guidance includes an updated list of  VOC sources in schools, and advice on minimising  children’s exposure, such as making a strong recommendation for  schools to carry out refitting and building work as near to the start of the  summer break as they can. “This will maximise  the chance for off-gassing while the  building is empty, so when the students return, the VOC levels have dropped as much as possible.”

Toxins have no “end of life”

Chemicals in building materials don’t stop causing problems when the building is no longer in use. These concerns were explored by Graham Winter, waste strategy and circular economy advisor at the Environment Agency. He discussed some of the problematic chemicals that have been incorporated into buildings over the years. These all cause issues when buildings are modified, dismantled or demolished, as the waste cannot go to landfill, or be used as hardcore.

Asbestos might be the best known example, buts more recent additions to the list include a number of persistent organic pollutants (POPs) – added into numerous products over the years, often as flame retardants. Materials that contain them are now classed as hazardous waste, with strict rules governing their disposal.

A common source of these compounds in demolition waste is polystyrene foam – POPs were added to these materials until 2016. “EPS and XPS insulation panels must be managed as POP waste. This means they have to be kept separate from other waste streams and sent for destruction.”  Graham warned that this was not as well known as it should be, and as a result, polystyrene was still not being disposed of correctly.

Anyone involved with deconstruction and demolition has to understand their legal duty of care, Graham stressed.  Employers also have an obligation to protect employees from exposure to toxic chemicals while deconstruction takes place. Meanwhile the toxic waste itself has to be disposed of in the approved manner, generally by being destroyed via high temperature incineration.

Another potentially toxic material is treated wood, as some previous treatments are now classed as hazardous. People should also beware newer materials that come from countries that have yet to implement bans, Graham added.

Design for deconstruction, specify for re-use

New additives are coming in to construction materials all the time, and could easily be the next problematic toxic chemicals when more is known about them. While new toxins may well eventually be banned, “it is a long process of collecting evidence, and even then, generally bans take place via phase-out rather than instant removal” – meaning inevitably, problems are being stored up for the future, Graham warned. So it makes sense to think very carefully about the nature of what is being put into a building in the first place – and ensure it is recorded.

Contamination with toxins – even if they weren’t considered toxins at the time of manufacture – makes it impossible to reuse or recycle materials. This is a direct hindrance to the circular economy. But even when individual components are not toxic, simply combining products –  putting a synthetic coating on a timber product, or producing pre-insulated plasterboard for example, also hinders re-use and recycling.

“We should be designing buildings for maximum useful life of the components, which means designing for deconstruction and  maximum re-use. Otherwise we are designing problems in for the future.” Graham said.  

“If we want zero waste from construction in 50 years time, then we have to stop putting things into buildings that are not reuseable, recoverable or recyclable, today”.  

Building components have much higher value – and a far, far lower carbon impact – if they can be retrieved and reused intact. But we can only do this if we know where to find them. The materials tracking app Qflow, which won a people’s prize in the ASBP awards is designed to solve exactly this problem. As Brittany Harris of Qflow explained “so many of the raw materials extracted to create building components end up in landfill. Much more could be reused or recycled – but we don’t know exactly what product is where.”

 Qflow gives each component a passport, to track the flow of all material on and off a construction site. It is integrated with whole life carbon tools, so can track embodied impact alongside this. The tool creates a real time record – it works  via a photo of the delivery note, and AI does the rest. It saves waste too: if the wrong product has been delivered, the mistake (or unwanted substitution) can be detected immediately, and rectified before the materials are used.

Deconstructing to build

As well as building for deconstruction in the future, we can deconstruct to build now. EMR Reusable Steel, another initiative shortlisted for 2024’s ASBP awards enables exactly this.

A large proportion of steel is recycled nowadays, and that sounds like a good thing. It is of course far preferable to smelting iron ore. But collecting, sorting, melting down and re-fabricating steel components is not a trivial exercise – it uses a lot of energy, emits a lot of carbon, and costs a lot of money. Yet so much of the steel in buildings that are demolished, is  perfectly good, solid, and structurally sound.

Tom Howarth of EMR described how the firm rescues re-usable steel. EMR works first with demolition contractors before demolition, to identify high-value steel components, then cleans and sizes the material for sale into new projects.

The value in the reusable steel makes it worthwhile to deconstruct carefully: “We are recovering the steel in its highest value form. This also means less emissions, less mining, and a more local supply chain.”

The most planet-friendly construction product of all, though, is the one you never need. It also saves the most money! Designing out unnecessary impact right from the start is the goal of another ASBP awards finalist, the Preoptima app. This app also capitalises on  AI  – in this case, to predict structures at the  crucial early stages of construction design, when changes cost next to nothing, and savings can be maximised.

The app uses the predicted structure to give  early insight into the likely embodied impact – and crucially, gives instant feedback on the impact on carbon totals of making changes.  As Preoptima’s Sarah Sexton told the meeting, significant savings can be made: “In a single project, we enabled to avoid over 2,000 tonnes of CO2e emissions through our early optioneering approach.”

Part 2: Buildings, timber and nature - at home and away

The ASBP has long championed the use of timber in construction. So it was heartening to hear Bella Murfin, Deputy Director for Trees, Woodlands & Forestry at the environment department  Defra, championing the cause in her keynote speech at the 2024 ASBP Healthy Buildings event. 

Bella set out how the UK government sees construction with home–grown timber as a way to reduce emissions, and support the much-needed increase in forest cover. She explained that increasing tree cover is essential for biodiversity, climate change mitigation, and climate resilience.

The England Forestry Action Plan has set a target to increase England’s forest cover from its current low level (not much more than 10%) up to 16%. Although still not a huge amount by many countries’ standards, this is seen as a “stretching” target by DEFRA, she said, but “good  progress” is being made.


Explaining the drive behind the timber construction road map, Bella said that timber in building should be encouraged, “as it is an inherently low carbon construction material”.

“The use of sustainably produced domestic timber in construction creates a market and an income stream for increasing our forested area,” she added. “This also makes economic sense. England imports 80% of its construction timber, and demand is expected to rise.”

In response, the government has created an innovation fund to support exploration of new techniques for using English timber, especially from broadleaves – for example, via thermal modification.

These keynote themes were enthusiastically taken up by other speakers at the event.

Timber, construction and the health of forests

 Joe Giddings, the UK Lead at construction network Built by Nature, updated the conference on the network’s activities, geared around mainstreaming the use of bio-based materials.

One huge benefit to bio-based materials is that most are inherently low carbon to produce, and in a building the carbon can be locked up for a long time, as well. Expanding on Bella Murfin’s comments, Joe pointed out that if our homes were made of timber instead of steel and masonry, we could avoid more than 100 billion tonnes of CO2 emissions by 2100. “This is about 10% of the remaining carbon budget for the 2 degree climate target.”

Built by Nature awards funding to help new product development, but also works with the “demand side” via networking and awareness raising – among designers, clients and specifiers, developers and insurers.

One of the biggest needs revealed across the sector is for reliable data. Built By Nature is working to strengthen traceability of timber products, to allow for easier comparison between them based on carbon footprint and wider ecosystem impacts. For example, the group is working to increase carbon accountability in the value chain of CLT in Europe.

A novel approach to assessing  the biodiversity in a landscape was shared by Emre Turhan of NatureMetrics. He described how NatureMetrics has developed a tool that works like a forensic detective. They take soil and water samples from the location being studied, and analyse them for traces of DNA. This way, they can to work out which creatures are present without anyone having to wait around to spot them. 

NatureMetrics’ library of DNA includes familiar species such as otters and hedgehogs, but also thosevital mini- and micro-organisms that in a resilient ecosystem, balance soil and plant health, and power the cycle of decomposition and regrowth.

Managing for biodiversity

The importance of understanding and managing the ecosystem impacts and carbon footprint of forestry was acknowledged by Mila Ducheva of Stora Enso. One of the world’s largest international forestry companies, Stora Enso owns or manages a lot of forest in Northern  Europe, but also right across the globe. The forests produce construction timber and timber products, and a lot of cardboard and packaging.

Stora Enso has started to write biodiversity protection into its long-term forestry strategy, Mila Duncheva explained: “We use native species where we can, and have a breeding programme to select  for climate resilience. We protect watercourses in our forests by leaving buffer zones, and allow spontaneously regenerated deciduous trees to remain. Some deadwood and selected trees of high nature value are left standing too, as these form valuable habitat for invertebrates, birds and animals.”

“Forestry is a long term process and we plan on a 100-year cycle. This allows us to develop mixed age stands – these are more resilient,” Mila said.  

Getting the biodiversity word out

The kind of information shared by Mila Duncheva should be in everyone’s mind – client, specifier and assessor. Raising awareness and increasing accessibility of this information is the aim of the IMPACTT timber transparency programme. The projects is led by ASBP with funding from Built by Nature, and ASBP associate Dr. Asselia Katenbayeva described how one of the IMPACTT projects  is setting out to do this.

“In construction we know very little about forestry, this project aims to bridge that gap,” Asselia explained. “Taking some timber buildings, we will follow the supply chain back to the  forests of origin, then try to identify carbon impact and biodiversity conditions there. We will then upload the data to a source map, where it can easily be seen by anyone.”

The buildings will be located on the map, and clicking on the building will link to the forests where the construction timber originated. “Then, you can click on the forests to learn about carbon and biodiversity in those forests.”

The long term aim is to make information about sustainable forestry practices and the origins of timber available to specifiers as standard: “We have partnered with timber certifier PEFC; despite being a very large certifier for sustainable forestry PEFC do not yet include biodiversity information in their certification process  – we are working with them  to help make this happen.”

Specifying for diverse and resilient woodlands

Dainis Dauksta Managing Director, Wood Science Ltd and Specialist Advisor at Woodknowledge Wales,  took us right back into humanity’s long history of shaping the landscape and coexisting with nature.

“How many wooded landscapes have been shaped, subtly or starkly, by human intervention?” he asked. “How do we respond to these landscapes emotionally?”

Dainis explained how, by shaping and managing wooded landscapes over centuries, humans have created new niches that humans and wildlife alike are drawn to; a theme echoed  by the speakers on biophilic design.

Dainis challenged the idea that a spruce plantation was a dead landscape, pointing to the presence of wildlife and of ferns, mosses and fungi, as well as natural regeneration where trees have fallen or are felled. He added that in Wales sheep grazing was a much more significant threat to biodiversity. “Spruce cover in Wales is just 4% of the landscape, whilst sheep farming accounts for 80%. Only 5% of welsh lamb is actually eaten in Wales – but sheep farming has led to precipitous drops in biodiversity.”

He pointed out that the UK is the second largest timber importer in the world. “We don’t even make full use of the timber we have. I say grow your own spruce, don’t demonise it.” However, landscape-scale change is seldom easy. Referring to recent protests in Wales over new obligations on Welsh famers and landowners to increase forest cover, he warned that policies must be introduced in a way that works for farmers. Change can only succeed if everyone is brought along.

Like other speakers, Dainis urged the industry to consider a wider range of tree species for construction. He suggested that lime has potential in construction. “It can be managed to grow very tall and straight, and the timber is durable – strong, and woodworm resistant. And the tree itself is relatively resistant to drought, which may be a great advantage in an uncertain climate.”

The wider benefits from a more diverse forestry were at the heart of  Jez Ralph ‘s talk. Jez, director of forestry consultancy Evolving Forests, challenged the construction industry to widen its horizons for the sake of our forests: “We are very focused on uniform material like CLT – and clearly that does make for a relatively quick easy task for the designer.”

“However we also should consider that to supply homogenous materials tends to need single aged single species stands, which are a lot less biodiverse, and can be more vulnerable to disease or storms.”  

There is scope to use a wider range species and less regular timber in construction, and a market for this would support more diverse forestry, and also reduce waste.

A mix of different species and ages gives the forest resilience now, and gives us more options for a timber supply in an unknown future. At Hooke Park, the Architectural Association’s woodland campus in Dorset, the maturing woodland has at least 15 species in a mosaic of stands. Could this be the future of timber production?  “We don’t know if it will all be useful,” Jez pointed out, “but if we want resilience this is what has to happen.”

Jez described some pioneering ‘non-standard’ timber sources already in use, such as thermally modified sycamore and poplar – and even, arboricultural arisings: “There is some beautiful wood from urban trees that would otherwise go to landfill,” he said.

Bridging the gap between non-standard timber and sound design was “a design challenge and also an engineering challenge,” Jez said, but he believes we can succeed.

Timber and biodiversity on site - bringing the power of nature into construction

Several speakers shared with the audience beautiful timber-rich buildings they had been involved with designing or building. They explained how the projects featured benefited from the practical advantages of timber construction. Timber buildings are fast to erect and often lighter than masonry, meaning less concrete in the foundations – and hence – a lower embodied impact as well as a swifter programme.

Equally impactful though, was the benefit of the experiential qualities of a natural material like timber in the indoor environment, especially for vulnerable groups of building users.

Dayo Shittu-Balogun, director of projects  at Eurban, introduced some of Eurban’s newest mass timber projects.

The practical advantages of mass timber were used to the full to create a secondary school campus in the rapidly expanding city of Cambridge. The buildings feature a lot of exposed timber indoors, and distinctive colourful exterior. Dayo explained how the significant element of offsite construction enabled a very rapid process on site, with the building rapidly becoming weathertight, enabling interior fit-out to proceed at a pace.

Dayo also described a rehabilitation centre in London constructed by Eurban. The Hope Street centre is part of the criminal justice system; it is a place for women serving community sentences, who have also suffered trauma, or whose living circumstances are dangerous.

The centre provides a safe place for the women to live during their recovery and rehabilitation, and the timber is an important element of the nurturing feel of the building. The centre has beautiful chapel-like counselling spaces, the high vaulted ceilings rising to a skylight, all lined out with timber to create a calm, protective, healing space.

This nurturing properties of timber are also present in Beormund primary in London, for children with social, emotional and mental health needs, again featuring natural materials, calm colours and refuge spaces, Dayo explained.

The nurturing and calming properties of timber and of nature have been used to the full in therapeutic buildings designed by Cullinan Studios. Partner Lucy Brittain introduced the Catkin Centre and Sunflower House, built at Alder Hey Children’s Hospital, as well as a new annexe for Maggie’s Newcastle. 

The Alder Hey buildings are dedicated to supporting children’s mental health – one as an outpatient facility, and the other a residential building that has to be secure, but also a healing space.

“The buildings use a lot of exposed timber, and have planting right up to the windows, to try to make a non-institutional space.” Lucy added there are also practical advantages to this in a building where patients may express their distress physically.  “Timber finishes are lower maintenance than plasterboard – CLT is a lot harder to damage.”

There is now high-level recognition of potential benefit of nature-rich construction, especially for young people.  Biophilic design has been the subject of intensive research and development by the architecture team in the Department of Education, led by architect Crawford Wright. To test out the learning in practice, the DfE architecture team went on to design and construct a purpose-built biophilic primary school in Derby, to replace a building destroyed by arson.

The previous building at St  Mary’s school occupied just one end of a generous site, and the design team were able to relax the new plan and weave outdoor pathways, and courtyards enriched with planting, right through the heart of the campus – while still retaining ample space for sports fields and play.

Crawford Wright’s colleague Meaghan Kombol , sustainability design advisor at the Department, explained how the landscaping design at St Mary’s aims to create  edges and niches that children are naturally drawn to.  These are exactly the landscape features highlighted by Dainis Danuska as being so important in landscapes that that feel like home.

Even on more compact sites, the potential for bringing nature not only to students, but the communities around them, is huge, Meaghan added. Almost 90% of the land in the education estate is outdoors – grounds, parking and circulation. How much nature could schools  bring into the urban environment, if all school boundaries were planted with trees and shrubs, she asked?

Nature is important to us all – even if we are working with bricks and blocks and not timber. Maisie McKenzie is Biodiversity Manager at brick, tile and paving company Wienerberger and her task is to embed biodiversity and biodiversity protection into the company’s operations.

Maisie explained that Wienerberger are  attempting to measure and record biodiversity net gain on their own land and on project sites: “When we are on site for a big project we partner with local wildlife organisations. And we are working with our own staff to empower them to discuss biodiversity with customers – we found an amazing amount of knowledge and enthusiasm for nature and wildlife already present in our staff teams.” This approach has not only accessed unexpected levels of expertise for the company – it has proved very rewarding for the staff as well – good for them, and good for the company too.

It goes to show that there is no part of the construction industry where prioritising nature and biodiversity are not important, relevant and ultimately rewarding.

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