AJ Climate Champions Architects’ Journal

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 david.watson@akt-uk.com.
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.