Operational Net Zero Carbon for new buildings
What it means, and four challenges for architects…
The operation of buildings is estimated to account for around 30% of the UK’s total carbon emissions, primarily from heating, cooling and electricity use[1]. If we are to meet our national climate change targets then by 2030 all new buildings must operate at net zero carbon – and that means a radical change in the way we approach their design. But what does operational net zero carbon mean in practice – and how can we, as architects, help to achieve it?
If a building is to operate at net zero, it must somehow regulate its temperature and power its lighting and appliances without contributing a positive amount of carbon emissions in the process. That seems a daunting prospect for residential buildings; even more so for more energy intensive ones like schools or offices – which is a reason why attempts to achieve net zero have typically relied on carbon offsetting, with all the attendant uncertainties and opaqueness.
But what if a building could achieve a genuine energy balance, producing enough of its own renewable, low carbon energy to cover the energy it uses, thus removing the dependence on offsetting? That goal is now within reach, but getting there requires a combination of technological, engineering and design expertise – all of which can be brought together by architects.
Designing for operational net zero carbon - three levers
When creating a operational net zero building, architects effectively have three ‘levers’ available to them:
Conservation – technologies to minimise the building’s energy demand, such as through efficient insulation and ventilation
Generation – on-site renewable energy sources to provide the building’s energy supply, such as PV solar panels or wind turbines
Design – optimisation of the structure and layout of the building to incorporate these energy conservation and generation technologies, and to make the building as energy-efficient as possible.
In practice, architects must model multiple iterations of the project design, calculating the energy balance each time and deploying these three ‘levers’ as needed until they reach an optimal result: one that not only achieves net zero but also meets all the many other practical and aesthetic requirements of the client.
This is no simple matter and designers must consider complex, intertwining factors.
[1] Committee on Climate Change (2018). Reducing UK emissions – 2018 Progress Report to Parliament.
Operational net zero: four challenges for architects
Here are four particular challenges that architects must address
1) Energy use must be kept to one-third of the maximum demanded by current building regulations
The minimum energy efficiency levels demanded by current UK building regulations are not adequate for realistically achieving operational net zero. Instead, designers need to aim for the targets identified by LETI. For residential buildings these are a Space Heating Demand equal to or less than 15 kilowatts per square metre per year; and a total Energy Use Intensity (EUI) – meaning the energy use measured at the meter – equal to or less than 35 kWh/m²/yr. (Alternative EUI targets exist for non-domestic buildings.)
This means that architects must have the tools to calculate EUI as they model projects, and the technical expertise to make adjustments – for example, to the building envelope, ventilation, and insulation – until the LETI targets are met.
2) No fossil fuels must be used in the building’s energy supply
Heating and hot water should not be generated using fossil fuels, while on-site renewable electricity sources such as PV panels or wind turbines must be maximised.
Architects will need to master the incorporation of new technologies like heat pumps and battery storage, and explore heating innovations such as imaginative uses of waste heat.
3) A zero carbon energy balance needs to be achieved – and then measured annually
Since the goal is for operational net zero, it’s essential that new buildings continue to achieve a net zero balance between energy use and supply when in use over the long term. An annual calculation needs to be undertaken to demonstrate that an ongoing net zero balance is still being achieved.
4) Meeting net zero affects the way buildings look
The use of the third architectural ‘lever’ – design – will have implications for the way net zero buildings look and feel. The need to accommodate sufficient solar panels may result in structures that are simpler in form and lower-rise. Their design might need to avoid overshadowing to maximise heat gain from the winter sun. They might use less glass but optimise sunlight through orienting windows.
The above diagrams illustrate some of the Passivhaus principles and are sourced from: Net Zero Toolkit by Levitt Bernstein, Elementa, Passivhaus Trust and Etude commissioned by West Oxfordshire, Cotswold and Forest of Dean District Councils, funded by the LGA Housing Advisers Programme
Architects will need to find ways to design beautiful, practical buildings that incorporate all the necessary ingredients for zero carbon.
Meeting the net zero challenges
In the coming years, the challenge will be to develop designs that balance all these criteria while also delivering beautiful buildings that meet the myriad practical demands of clients and local communities.
At Cullinan Studio, we believe that the building principles laid down by Passivhaus provide a key for architects to unlock operational carbon net zero for new buildings. We explore these principles in this article: How architects can use Passivhaus principles to unlock operational carbon net zero
But further challenges lie ahead with adapting and retrofitting older buildings to become more carbon efficient. And as complex as operational net zero is, it is only one piece of the net zero carbon puzzle, which also includes reducing emissions in construction, limiting embodied carbon, ensuring the lifetime durability of buildings and developing the circular economy and smart local energy systems.
We look at how we architects can address these issues in this article: 6 ways architects can help achieve net zero carbon in buildings.
Achieving operational carbon net zero is one of the biggest and most important challenges facing architects, and one with a wide range of implications for designers, clients, engineers and all stakeholders in new buildings.
Partner Lara Michael is a Certified Passivhaus Designer. If you would like to discuss any of the issues about operational net zero carbon raised in this post, drop Lara a line.
See also: