‘Over-specification of concrete is an industry addiction’

Episode 52. AJ Climate Champions with Hattie Hartman and Joe Jack Williams.  To achieve replication at scale, Nicolas Coeckelberghs of Brussels-based BC Materials favours compressed earth blocks over rammed earth. ‘Our goal is to bring earthen construction from a niche to a growing market,’ says  Coeckelberghs. He likens this challenge to playing chess on multiple fronts, creating demand while simultaneously supplying the market. While acknowledging the aesthetic appeal of rammed earth,  Coeckelberghs cautions that it is technically complex and unaffordable at scale. In this episode, Coeckelberghs describes BC Architects’ 15-year trajectory from its first earth building in Burundi, to the proliferation of collaborative workshops which led to a strand of consultancy work, to the creation of cooperative BC Materials in 2018. This led in turn to the recent launch of Léém, a manufacturing company that produces circular materials: unfired bricks, and clay plasters and paints. While  Coeckelberghs is an innovator, he is also pragmatic and advocates focusing on easy wins. ‘Don’t use earth to make facades, just use it to make structures inside,’ he says. He sees enormous scope for application of earth blocks internally where they are protected from the weather and hence more durable. In search of a way to scale the earth blocks production, BC Materials visited concrete and brick manufacturers across Belgium to understand their manufacturing techniques and explore possibilities for collaboration. Partnerships with large manufacturers are now underway, and BC Materials produces its blocks through  ‘industrial co-working’,  using the larger plants’ production line during their ‘off’ hours. For show notes and to catch up on all AJ Climate Champions episodes, click here.

Episode 51. AJ Climate Champions with Hattie Hartman and Joe Jack Williams.  Daniel views mud and waste as opportunities, not obstacles. He advocates an approach of ‘maximum optimism’, explaining that mud and waste enhance his designs. ‘I follow the materials; they do not follow me,’ he says. Sourcing materials primarily from within five miles of a site, Daniel describes how mud and waste can be transformed into beautiful buildings. But this was not the case from the outset.  Daniel first incorporated waste bottles into an early project because the budget ran out before the windows had been purchased. He then realised that a new aesthetic had emerged from this approach. Daniel argues that architects need to be on site, not in the office, in order to observe their surroundings. ‘Open your eyes. Be out there!’ he advises. Architecture is not a white collar job; it’s about going to site, according to Daniel. ‘Today architects are not able to see because we are simply oblivious to what is happening around us. This way of practice has to change,’ he insists. Daniel’s ambition is to bring earth construction to the mainstream and he is not opposed to adding small amounts of cement to his earth mixes to increase structural strength. ‘We need to enter commercial construction. If that means using a bit more steel or cement than the purest form of mud architecture, I’m open to it,’ he says. For show notes and to catch up on all AJ Climate Champions episodes, click here.

Episode 50. AJ Climate Champions with Hattie Hartman and Joe Jack Williams.  Carmody Groarke sustainability lead Sian Ricketts explains how architecture can adapt to the reality of finite resources and an abundance of waste. Ricketts says that architects should develop their intuition and new rules of thumb to design for a changing climate. Architecture needs to adapt to incorporate materials from waste streams, and this requires a new approach to detailing and ongoing maintenance. ‘The industry is going through a huge learning process and we should not be scared of getting it wrong,’ she says. Marginal gains on every project are important. In this episode, Ricketts describes the process of developing a bespoke brick for the Design Museum Gent in Belgium. She explains that the practice did not start with a bespoke brick in mind. Because conventional clay-fired bricks are high in embodied carbon, an exploration of less carbon intensive alternatives led to an in depth collaboration with Local Works Studio and Brussels-based bcmaterials that in turn led to incorporating local waste streams into the design of the new brick. Ricketts observes that the process of developing the bespoke brick for Ghent has strengthened the practice’s confidence in seeking opportunities for both innovation and circularity in future projects. Carmody Groarke is currently working with Imperial College-based startup Seratech to explore the use of magnesium carbonate as a binder for bricks. For show notes and to catch up on all AJ Climate Champions episodes, click here.

Ep 49. Structural engineer David Watson describes the enduring appeal of brick and its underexploited superpower: reuse Brick has many advantages: durability, aesthetics, use as both envelope and structure, and the possibility of local (even artisanal) production. This last point differentiates it from steel and concrete, due to the Ordinary Portland Cement needed for concrete production. ‘We need to ‘build our intuition about what impacts embodied carbon and emissions from different materials,’ says Watson. Watson highlights the importance of querying the firing required to achieve different finishes, because it varies between brick types and can significantly impact overall embodied carbon. It’s also important to understand the fuel used in the kilns where bricks are fired.  While in the UK this is predominantly natural gas, abroad it might be charcoal or coal, both of which generate significant amounts of particulates. In non-loadbearing cladding applications, the embodied carbon of the support systems must be taken into account because they can comprise as much embodied carbon as the brick and mortar combined. These hidden impacts are often difficult to calculate due to lack of EPD data, explains Watson. Brick reuse is on the increase but currently comprises less than five per cent of the market because of the challenge of removing the mortar, particularly those bound with Ordinary Portland Cement. Traditional lime-bound mortars are easier to remove. Current research is exploring mechanised removal of cement-bound mortars, and increased demand should prompt the market to respond, says Watson. In this episode, we also discuss ConcreteZero targets (AKTII is a signatory) and the extent to which they rely on GGBS. Watson stresses the necessity of ‘using less’, for example, exploring ribbed, coffered or troughed slabs as an alternative to flat slabs. He advocates form-effective design, marrying structure with architectural expression in a lean use of materials. David Watson can be contacted at [email protected]. To catch up on all episodes of AJ Climate Champions, click here.

Episode 48. AJ Climate Champions with Hattie Hartman and Joe Jack Williams. Structural engineer Eva MacNamara of Expedition Engineering explains how we can radically reduce our use of concrete and how to better understand the biodiversity impacts of material choices. In this episode, we dive into the tricky topic of concrete and unpick the widespread mantra that ‘concrete is bad’.  Concrete is ‘an addiction’ that has led to an obese construction industry, says Expedition’s MacNamara; it is not going to go away but we can radically reduce our use of it. She describes a porposed slab design for the Eden Project site in Dundee which would achieve an 80% reduction in concrete volume. MacNamara stresses that ‘using less’ is much more impactful than substituting low-carbon concretes and notes that she repeatedly sees practitioners over-specifying. We discuss some of the nuances of concrete use: which applications are most appropriate, how to reduce the volumes we use, and why low-carbon concrete – especially GGBS – is not a silver bullet. We also touch on upcoming innovations including Seratech, ‘funnel’ slabs and smart crushing. McNamara explains how to bring both carbon and biodiversity into the concrete procurement process. Highlighting findings from the recent report The Embodied Biodiversity Impacts of Construction Materials (Expedition/ICE, November 2023), she notes that 95% of biodiversity impacts occur off site and that the new biodiversity net gain requirements only address the 5% on site, so designers must look beyond a site’s boundary. Finally, MacNamara advocates finding a place to innovate on every project. ‘We can make the most difference by using our projects as springboards for incubating innovation,’ she says. For show notes and to catch up on all AJ Climate Champions episodes, click here.

For the first in a new six-part series on materials, Hattie is joined by co-host Joe Jack Williams to interview Martha Lewis, head of materials at Danish practice Henning Larsen. Lewis argues that a baseline of health and environmental impacts should inform material specification, and explains why a holistic approach is essential to navigate the nuances of material selection. She describes how the European focus on life cycle analysis and the Global Warming Potential of materials is starting to be integrated with the earlier American focus on healthy materials and toxic chemical content. ‘The glut of information is a challenge of our time. How do we navigate too much information to make the right decisions?’ asks Lewis. She advocates for material passports which would consolidate the relevant data needed to make informed decisions: carbon emissions, chemical content and circularity. She also argues that certification schemes, despite their weaknesses, are the most effective route to ensuring that a project delivers on its sustainability aspirations. Also in this episode, Lewis describes Unboxing Carbon, a database with an accompanying course which she has developed to upskill architects on the carbon aspects of material selection. Lewis has rolled out Unboxing Carbon across Henning Larsen’s 700-strong practice and also offers it to external practices. For show notes and to catch up on all AJ Climate Champions episodes, click here.

Episode 46. AJ Climate Champions with Hattie Hartman and George Morgan. Andrew Waugh explains how building with timber can address industry transformation at scale. ‘I want to transform the whole industry,’ says Waugh, founding director of Waugh Thistleton which was recently named Practice of the Year at the AJ Architecture Awards. In this episode Waugh explains why tall buildings have no place in sustainable cities of the future; how building housing with timber can reduce its carbon burden by as much as 75%; and why we should stop building basements (they are up to five times as carbon intensive as upper floors). Waugh advocates building with timber primarily as a low-carbon alternative to concrete and steel, rather than for aesthetic reasons. He shares recent research that clarifies end-of-life alternatives for timber that are not incineration or landfill. He makes it clear that current subsidies that encourage burning of timber for biomass must be revamped to support use of UK-grown timber for construction. This episode was recorded the day after Waugh toured co-hosts Hattie and George through Waugh Thistleton’s recently completed Black & White Building in Shoreditch. The building is nearly all timber: structure, core, floors, cladding and brise-soleils. Waugh describes where the timber was sourced and that the transport footprint of timber is a relatively minor consideration. Finally, Waugh explains why he recently withdrew from the Architects Declare steering group. For show notes and to catch up on all AJ Climate Champions episodes, click here. With support from the American Hardwood Export Council A previous version of this podcast mistakenly suggested that Waugh Thistleton had withdrawn from Architects Declare. In fact, Andrew Waugh withdrew from the Architects Declare steering group in May on an individual basis and Waugh Thistleton remains a member of Architects Declare. We apologise for any confusion.

Episode 45. AJ Climate Champions with Hattie Hartman and George Morgan. Two Public Practice associates explain how working in the public sector has increased their agency as designers. Public Practice is a social enterprise that places built environment professions in the public sector, primarily in place-making roles and increasingly in key roles that drive retrofit and net zero. ACAN co-founder Lauren Shevills, now lead retrofit innovation and delivery officer at Westminster City Council, explains that Public Practice has changed the trajectory of her career, enabling her to marry her passion for community and stakeholder engagement with technical architectural expertise. Steve Westcott, low carbon programme manager at Greater Manchester Combined Authority, says Public Practice has empowered him to work more strategically and ‘be closer to the conversations’ that matter. Off the back of Westcott’s role, GMCA is recruiting additional Public Practice associates. On the subject of retrofit, Shevills observes that one major challenge is that retrofit cannot be mandated because it’s currently not part of the planning process.  A retrofit first policy requires a rethink of current guidance and Westminster Council has five workstreams underway to explore various aspects of retrofit. Westcott explains that a fabric first approach is often too costly. The GMCA is developing portfolio-wide data collection for the city’s non-domestic estate to inform future grant disbursement decisions. For show notes and to catch up on all AJ Climate Champions episodes, click here.

Episode 44. AJ Climate Champions with Hattie Hartman and George Morgan. Studio Weave founding director Je Ahn explains the challenges of sourcing timber from London’s streets and parks. He describes how he translated the ambition of using local timber from London’s trees into reality at Lea Bridge Library Pavilion despite the fact that no sales channel existed for sourcing local timber and the need to prove its chain of custody because it had no FSC certification. We also discuss how working with found materials requires a willingness and ability to improvise as a designer and creates new aesthetic opportunities. In the case of Lea Bridge Library Pavilion, this approach lends warmth and informality to the space. ‘You have to be ready to change your mind to suit the requirement,’ says Ahn. Ahn describes sustainability as project-specific. ‘I’m very interested in where we get our materials,’ he says, explaining that timber is not always the best solution. It’s all about achieving the right balance for a given project. ‘Whatever I put out in the world has to have a purpose beyond what was initially set out,’ says Ahn. For show notes and to catch up on all AJ Climate Champions episodes, click here.

Ep 43. AJ Climate Champions with Hattie Hartman and George Morgan. London Eye architect Julia Barfield explains how the climate emergency changed the way her practice, Marks Barfield, operates, as well as what’s ahead for the Architects Declare movement. Julia shares insights from recent projects on how to achieve circularity in retrofit, the challenges of stockpiling materials for reuse  and how Orms’ material passports can be adapted for retrofit. ‘We must treat all materials as the precious resource they are,’ she says. She talks about her practice’s Stirling Prize-shortlisted Cambridge Mosque, which is part of a Built by Nature-funded post-occupancy study evaluating the quality of life and performance aspects of five CLT buildings. We also speak to Julia and fellow Architects Declare steering group member Zoe Watson about what AD has achieved four years on as well as its current workstreams, including climate emergency training for design review panels and Meet the Steering Group sessions where AD signatories can seek practical advice on how to further sustainable design within their own practices. As part of an ambitious strategy for change, AD is launching a three-part roadmap aimed at equipping Government policymakers with practical and impactful policies to reduce emissions, kickstart the circular economy and restore social and natural infrastructure.  AD plans to launch its document in Parliament in 2024. For show notes and to catch up on all AJ Climate Champions episodes, click here