This article is based on the Built Environment Matters podcast episode that featured Bryden Wood's Head of Sustainability, Helen Hough.

When we talk about the sustainable design of buildings, we have two core objectives: reducing environmental impact, and providing a healthy space for occupants. For this reason, implementing a sustainable design strategy incorporates every aspect of the building process, from the earliest design stages through to construction and post-completion. Evaluating an asset’s performance, and understanding how its entire environment operates, forms a key part of our work within Sustainability and Building Physics at Bryden Wood. We look at how a building gains heat in summer, or loses it in winter; how it requires natural or artificial light; as well as issues like temperature control, moisture and air movement. Although some of the focus on this topic was lost in the last recession, the industry’s renewed commitment to sustainability in design is intensifying. This is in large part due to the climate emergency and our need to achieve net zero carbon emissions by 2050. However, it’s also due to our simple desire to create the best buildings we can; those which promote health and well-being for occupants, and are comfortable, durable and safe to use.

WELL building standards and passive design

As in so many other areas of our lives, COVID-19 has created new challenges within the architecture and design space, with clients now regularly requesting COVID-secure design. The idea of designing for COVID is very compatible with sustainable design’s broader focus on health and wellbeing, and ties in nicely with the WELL Building Standard. This American rating system, launched in 2013 and now in the UK, challenges the built environment from a wellness perspective, while the UK’s earlier environmental assessment method, BREEAM, also places some attention on things like thermal comfort and air volumes. In the case of designing for COVID, the most obvious starting point is to look at the airflow of a building — how it might move through an office floor plate, for example. Here, computational fluid dynamics (CFD) offers us a way to address the challenge using a process based on mathematical modelling.

Passive design measures also form a key part of a sustainable design strategy. We must consider elements such as building orientation, the optimisation of facades to balance seasonal heat loss and gain, enhancing daylight and using natural or mixed-mode ventilation. To truly achieve sustainability in design, we should use passive design measures as much as we can to address health and wellness related challenges, as we search for a balance between wellness and energy efficiency. If we’re pumping air into our buildings to make sure the environment is clean, are we wasting energy? Focusing on sustainability in design with passive design measures can help us rely less on mechanical systems. When we do use them, it’s important to make sure they’re energy efficient — they need to be properly designed, set up and commissioned.

Construction technology: data and computer modelling

As time progresses and construction technology advances, the importance of data and computer modelling in sustainable design continues to grow.  A few years ago, we had only very basic computer modelling to help us understand what to expect from a building’s energy performance. These days, additional layers of data are being added in, so that our design decisions are really being driven by data now. This enables us to make better, sustainable design choices, and to improve a building’s performance right from the start. We look at issues such as the material choice for a building’s facade and structure, as well as energy performance and thermal comfort. These are evaluated with respect to the passing of time. What will happen year on year, and at the end of a building’s life?

Embodied carbon in sustainable building design 

One of the core issues we’re trying to tackle with sustainable design revolves around carbon. We know a lot about operational carbon and how buildings operate. Data helps us to close the performance gap and make sure buildings perform as well as, or even better than, they do in the design stage. As we’re able to drive better and better performance through energy efficient equipment and passive design techniques, we can actually start reducing our operational carbon right from the early design stages. This decrease in operational carbon will continue over time with things like the decarbonisation of the electricity grid. However, the result is that embodied carbon in buildings, due to material usage and the amount of carbon which is integral to the building itself, becomes a larger proportion of the overall carbon emitted from the building across its lifespan. As such, embodied carbon is increasingly playing a much bigger role in our day-to-day focus on sustainability as architects and designers. 

Embodied carbon varies based on the building typology. For example, in residential architecture, we might see a ratio of one third embodied carbon to two thirds operational carbon across a building’s lifespan. On the other hand, with a building like a data centre, where the operational energy of the building is very high, operational carbon will always be a larger portion of the total, whole-life carbon of the building.

The good news is that our data is improving all the time, and the industry is gaining momentum around the issue of sustainability with respect to embodied carbon. Within the next couple of years, we’re going to see an amazing increase in knowledge. Project life cycle assessments (LCA) are becoming standard practice. Five years ago, that simply wasn’t the case for most consultancies. There’s also a lot more guidance around now, for example, from bodies like the Chartered Institution of Building Service Engineers (CIBSE).

Sustainable building materials and platform construction

One topic which must be addressed in relation to the reduction of embodied carbon is the sustainable use of building materials. This is an issue we’re particularly focused on at Bryden Wood, in our work with Platform construction. This transformative kit-of-parts approach enables a reduction in the quantity and weight of building materials. With Platform construction we know exactly which components will go into a building. As a result, we’re able to give considerably more care and consideration to the design, procurement and construction of each individual part. Platform construction offers us a wide range of improvements when compared to traditional construction — it’s faster, safer and more cost effective, for a start. However, one of the biggest benefits Platform construction offers is to give us more control, which ultimately facilitates meaningful embodied carbon savings.

When we look to use sustainable design techniques to reduce embodied carbon in a building, we first seek to reduce the quantity of building materials used. After this, we evaluate the material type. Although we do look at traditional building materials, like steel and concrete, it’s also important to evaluate how specifications might be changed and adapted for newer product options, such as low-carbon concrete. Future proofing is a consideration, because when new materials and improvements in the industry arise, we want to be able to make best use of them without having to substantially change designs. We don’t want to have to rearrange all of our architecture, just because there's a new product available. We can overcome this issue by designing flexible buildings, offering future use suitability to a number of different architectural typologies.

The benefits of kit-of-parts architecture

Another benefit of a Platform construction, kit-of-parts, approach is that it’s very deconstructable. We don’t need to use hot welding on-site. We have reversible jointing methods. This means that the building can be dismantled in pieces, which extends the life of components because of the potential for reuse on the next building. Therefore, construction Platforms include an improvement to efficiency and sustainability across multiple buildings, for years to come.

The future of net zero carbon emissions

These days there’s a lot of discussion within the sustainable design space about targets for a future net zero state, and how that relates to both operational energy and embodied carbon. There are numerous benchmarks and targets in place for operational energy. These include UK Green Building Council (UKGBC) targets for offices, as well as London Energy Transformation Initiative (LETI) targets for various building typologies. These metrics generally look at energy rather than carbon. This is partly because we know the electricity grid is going to be decarbonised. Therefore, using electricity as our primary, or only, source of power on-site means we’ll be tracking alongside the decarbonisation of the grid. That’s well known in the industry; there’s guidance in place and our focus on sustainability in design has meant that we’ve been working towards that for years now.

Grid electricity carbon factor

The electricity grid had a much higher carbon factor a few years ago than it does now. This is due to coal plants, etc. However, substantial development and investment in recent years by the government and private bodies has reduced the carbon factor of the grid, through the use of renewables, nuclear power stations, and so on. The National Grid is responsible for working out the carbon factor for the entire grid. They have scenario modelling and are aware of where things could end up in the best case scenario. However, they also look at what’s happened over the last year. This means we know what’s happening in the UK in terms of energy balance. We can use that data when considering sustainability in our designs to give a very detailed, current understanding of what the electricity grid is, and what that means for buildings.

We can also use their predictions to understand how the grid is going to decarbonise over the next five to ten years. Importantly, the trajectory for that decarbonisation looks healthy. What it really comes down to is different scenarios, related to levels of investment, and what that will consist of. Decarbonisation of the electricity grid is a very large-scale endeavour. Massive wind turbines, all the way through to the PV panels on individual homes; all of these elements contribute to the electricity carbon factor and will play an important role in creating a more sustainable future.

Net zero by 2050

It’s true that not every building is going to be net zero at the moment. That’s alright. We’re designing with the government’s 2050 net-zero carbon objective in mind, and we’re on track to meet that goal. We’re designing to maximise use of the decarbonised grid. The foundation of our approach to sustainability is based on using lean, passive design methods. It’s only after passive design strategies are considered that we look at efficient equipment selections, renewable technology and low/zero carbon technology. In other words, when we look towards sustainable design, the focus on sustainable architecture must come before the focus on sustainable services.

Operational carbon - industry benchmarks

 The second part of the net-zero carbon equation is the operational carbon, for which there are currently fewer benchmarks. These are still in development by the industry. However, some have been released by LETI, RIBA and others, and there is an effort within the industry to get them aligned. What we need now is for organisations, clients and engineers to do the calculations to find out what the embodied carbon is within their building designs — both at the design stage and post completion. We need to be monitoring what is actually going into buildings, compared to what we think should be going in. This means that contractors need to get on board as well. Ultimately, we’ll have to collate the data together as an industry, but benchmarks will help us learn, and guide us at the design stage.

Creating a sustainable future — alignment of standards and guidance

One of the key challenges we need to address in our quest for a sustainable future, is to align the various forms of guidance and advice coming into the industry from different sources. There are currently a number of different institutions involved, all representing different parties within the built environment. While it’s positive they all have the same net zero goal, they offer different guidance. RIBA represents architecture and CIBSE represents engineers. Then there’s the London Energy Transformation Initiative (LETI) and networks like Architects Declare and Architects Climate Action Network (ACAN). The latter are more voluntary organisations, aiming to demystify some of the complexity around net-zero. They’re trying to push things from a legislation perspective. Legislation is important, because it leads to clear guidance which industry professionals can use in their day-to-day work. LETI have taken it upon themselves to look at embodied carbon in order to put into a single benchmark what the UK Green Building Council (UKGBC), RIBA, CIBSE and others are doing. It’s positive that individual institutions are there to provide very detailed guidance for specific consultants and professionals, but we also need to have an overarching look at where the industry is heading as a whole.

LETI and Design for net zero carbon

Last year LETI published some of the first documents offering advice on designing for net-zero carbon: The Climate Emergency Design Guide, and The Embodied Carbon Primer. A voluntary organisation made up of hundreds of professionals, LETI aims to share and collate knowledge in order to improve the way buildings are designed. Bryden Wood’s Head of Sustainability, Helen Hough, has been leading the embodied carbon workstream for the past year. There are now six sub-workstreams within it. Each one is looking at different aspects of embodied carbon: the importance of whole-life carbon, benchmarking, the collection of case studies, etc. The aim is to gather knowledge and offer industry advice.

As part of this effort, some data has been published on the Landsec/Bryden Wood project, the Forge. This ground-breaking P-DfMA office building project is currently being delivered on-site in London, featuring an almost 20% reduction in embodied carbon. It’s a fantastic achievement, and because The Forge is a Platforms construction project, we’ll be able to take what we’ve learned to create further benefits on future projects.

With the Forge, we’ve been able to prototype the project in advance of it going on-site. We’ve been able to look at things like different concrete mixes, relating to the self-compacting nature of the concrete. Through evaluation of embodied carbon, we’ve been able to offer lower carbon concrete mixes, tested before being transferred. In this case, Easispace put temperature sensors in the concrete, with mobile phone alerts indicating when the concrete became strong enough to strike the shuttering. This process of fine tuning the concrete enables it to be kept as low-carbon as possible, optimising it for strength, while still keeping the building process as quick as possible. It’s a good example of the improvements made viable with prototyping, which aren’t achievable when a project is live on-site for the first time. This transformational process of on-going refinement and progress isn’t possible in traditional construction, where every building is bespoke. It’s yet another benefit of a Platform construction approach, which helps us to achieve greater sustainability in design.

Addressing the climate emergency in construction

Currently contributing 39% of global carbon emissions, there can be no doubt that the construction industry has a serious and urgent role to play in addressing the climate crisis. The starting point is industry collaboration — a united focus on raising the industry’s understanding, knowledge and skills in relation to sustainable building. We need to be investing in colleges and universities, educating our young people and making sure they get the right training from the outset. We must have an industry-wide effort, focused on sustainability in design, one where we can all contribute, rather than having a few people in senior positions trying to force the issue.

We need to do more with passive design, whether it be a fully certified, Passivhaus approach, or simply using sustainable design features more generally from the start through to completion: early design stages, technical design, procurement and construction. Nothing lost along the way. We need to involve contractors and manufacturers, with contractors pushing their supply chains to make sustainability-led improvements in their products and materials.

Yes, there are challenges, but if this industry (not famed for collaboration) would commit to working together, they are surmountable. We’ve definitely seen an increase in collaboration in the past months. There’s a lot of enthusiasm around sustainability in design, but we need it to manifest. The next generation are incredibly aware of the climate emergency and these types of issues, but we can’t wait for them. If we wait any longer, we’ll miss the boat. The building blocks are in place and the time has come to make the change. It’s up to us to build our sustainable future.


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