The beauty of doing less

By something of a coincidence, there’s a lot of flying concrete in this issue.

To start with a generalisation, there are two reasons why an architect might need to stick their nose into how concrete is made: because they care about its appearance, or because they want to reduce its embodied carbon.

Much of my time is spent answering designers’ technical queries on each of these – and while they might seem like separate conversations, I’ve found that it’s very hard to discuss one without talking about the other. This is because it’s the cement content of concrete that is largely responsible for both its colour and its embodied carbon emissions. So when advising architects on visual finishes, I have always indirectly ended up talking about sustainability – in terms of cement replacements such as GGBS and fly ash. When the topic is sustainability, visual concrete often comes up too – not only because the composition of a mix affects its appearance, but because leaving concrete surfaces exposed is increasingly common as part of a holistic low-carbon approach.

By allowing the concrete to act as both structure and finish, and often fulfilling a range of acoustic and safety functions too, this reduces the overall amount of materials required, and the need for maintenance over the long term. And it can lower operational carbon emissions too, by tapping into concrete’s thermal mass to reduce demand for heating and cooling. The challenge here is that exposed concrete is not everyone’s cup of tea. It is traditionally associated with an industrial aesthetic, beloved in warehouse conversions, creative offices and funky retrofits, even though a quick flick through these pages, let alone CQ’s extensive archive, reveals myriad other ways to display it. This is a familiar conundrum that recurs in every other aspect of life, where halting climate change requires us to change our habits, preferences or tastes: it won’t work as well if it is perceived as a hair-shirt option.

Fortunately, there are as many ways to refine concrete’s appearance as there are to lower its carbon – which is to say a lot. The composition of this material and the way it is made is multifaceted and undeniably complex. As architects, we’ve never really needed to get into this level of detail, and it’s generally not been part of our training . But the pressing need to reduce carbon, and to ensure materials are responsibly sourced, means that we can no longer afford not to: the industry is steadily reducing the embodied carbon of UK concrete, but some of the biggest, unexplored opportunities for carbon savings using concrete are in the hands of specifiers – if they know how to seize them. Architectural education needs to be updated to reflect this too.

We can’t lose sight of the bigger picture: we are building not for its own sake but to meet a social need – for shelter, for education, for community or civic life – and if people don’t enjoy being in the spaces we’re creating, all our efforts (and a lot of materials) will be wasted. So if we are specifying exposed concrete as part of a sustainability strategy, we need to talk about how to make it beautiful too.

Elaine Toogood, Director, Architecture and Sustainable Design, The Concrete Centre