The AJ asked leaders in the sustainability field what immediate steps architects could take towards achieving a zero-carbon built environment in the near future
1) The default position should always be to retrofit existing buildings
Jonathan Tuckey, director, Jonathan Tuckey Design
The best way to reduce the carbon footprint of buildings is not to build them at all.
As an industry we must minimise demolition wherever possible and maximise reuse of existing structures. Radically transforming a building creates inspiring and joyful spaces which are full of both history and future promise.
As a profession, we must take it for granted that such retrofit schemes should be well insulated, well lit, airtight and sustainably heated.
We must minimise demolition wherever possible and maximise reuse of existing structures
This approach could be encouraged with across-the-board incentives. Remodelling an existing building is currently accompanied by 20 per cent VAT while it’s zero for new-build projects.
This should be reversed and the government could further subsidise the upgrading of a building’s thermal performance. It could introduce a carbon tax on materials or a carbon credit on recycled buildings, which might encourage people to recycle as much as possible. When you take a building apart in Switzerland you must separate out materials so they can be recycled. This is a very time-consuming process but the decision to demolish is taken with this in mind.
With some relatively straightforward changes to legislation we can prioritise and celebrate the reuse of existing buildings and make the process more profitable. Local communities would prefer to see their much-loved streets preserved; while making buildings more energy-efficient is better for the environment while reducing costs as fuel prices soar.
2) Reduce the use of concrete by three quarters immediately
Piers Taylor, founder, Invisible Studio
Concrete is the least understood commonly used building material. We know, of course, that concrete is the most widely used material on the planet. What is less known is that it is a relatively low impact material in CO2 terms.
If concrete is replaced by almost any other material, it would have a bigger carbon footprint. For example, using steel as a substitute for concrete is less efficient in CO2 terms, while most brick manufacturing processes produce more CO2 than cement production, including low-tech production methods still predominant in the developing world.
Although there are wider environmental implications, the main reason concrete has a big carbon footprint is because of the huge quantities used. But also, optimising concrete designed for construction is an inexact science. It’s almost impossible to determine the optimal concrete for many applications, meaning too much cement is used, and limestone-based cement requires huge amounts of energy to produce.
While ultra-strong concrete is being developed, allowing a more efficient use of material, ultimately we solve little through direct material substitution in any case.
If the construction industry is to make the necessary radical reduction in CO2 emissions, we need to change the way we design. This means designing leaner buildings that are planned in dense medium-rise communities where we can use timber for the bulk of superstructure. While it is difficult to use materials other than concrete for foundations, at the heart of our problem is the construction industry’s lazy use of concrete – using too much concrete with too little thought on structures that are badly designed, such as buildings that lack the resilience to adapt or are designed with little thought of how they might be adapted in the future and are pulled down after less than 40 years.
At a stroke, we could reduce the amount of concrete we use by up to 75 per cent if we were more strategic and only used it for essential aspects of construction that would last for more than 200 years, and instead used far more timber.
3) Understand how buildings are performing in use
Clara Bagenal George, senior engineer, Elementa Consulting
Understanding the performance of buildings that we have already constructed is the first step in better defining the challenge and understanding the steps that need to be taken to achieve a development that meets our climate change targets.
Whole-life carbon is made up of embodied carbon and operational carbon. The latter, the carbon emissions associated with a building’s day-to-day energy use, can be measured and understood through information from energy bills or meter readings. This data can be expressed as kWh/m2 and then compared against similar developments and published benchmarks.
These simple metrics will enable architects to better understand which buildings perform well in use and why, which will encourage them to engage with design solutions that can reduce energy and thus resultant carbon emissions.
Understanding the embodied carbon of built projects is equally important. BIM-based tools are available that make embodied carbon assessment easier and quicker, such as HBERT from Hawkins\Brown.
These help equip architects with the information needed to take ownership of a development’s whole-life carbon impact.
4) Treat embodied carbon with the same importance as gravity or sunlight
Simon Sturgis, founder, Targeting Zero Carbon
The embodied carbon costs of the materials and systems we choose for our buildings, perhaps surprisingly, make up the majority of a building’s lifetime carbon emissions. Architects are therefore in the position to be the true custodians of their designs’ carbon performance.
Low carbon and resource-efficiency go hand in hand, encouraging the use of recycled content, the reuse of structures and buildings, and the selection of renewable materials.
This requires a detailed understanding of the supply chain: what things are made of, where they come from and where they will be going at the end of a building’s life.
Architects require a detailed understanding of the supply chain: what things are made of, where they come from and where they will be going
Attributes such as long-term durability, adaptability, flexibility and designing for deconstruction and reuse (circularity) all have measurable carbon benefits.
When we design a building’s envelope, a full understanding of the relationship between in-use operational performance and the embodied emissions of the material choices not only enables the most carbon-efficient solutions but also helps us assess the future implications of climate change on our designs.
As this century progresses, these issues will become central to the way we design buildings and so have a significant impact on architecture.
5) Make sure every design has optimised massing and orientation
Anna Woodeson, director, LTS Architects
The days when buildings were built to resemble that napkin scribble an architect penned in his (always his) favourite restaurant should be over.
We need to work hard enough in the early weeks of the design process to ensure our buildings are also working hard enough. This is a necessarily iterative process. Is the building using more energy just because of its form? Does it have too much surface area or too much glazing? Is its thermal envelope easy to map and therefore to detail? Is its orientation optimised to ensure it is taking advantage of solar gain in winter but eliminating it in summer? All incredibly basic principles but in getting the massing and orientation right early, we pave the way for the possibility of net-zero buildings.
Software is developing to help us carry out more responsive analysis of the energy demand of our early models, but we find it is hard to beat the involvement of a proactive building physics engineer.
So this is not just about the rigour with which we approach our early design work but also about who we work with and how we procure buildings.
The architectural competition process, for example, often forces a building design in weeks, without the support of a wider design team. This does little to support the collaborative process required to develop a very low-energy building. Perhaps instead we should be judged on our proposed approach to a commission.