How the low-carbon active building works

A low-carbon approach known as the active building concept has now successfully integrated renewable heat, power and transport technologies, supporting the existing energy network by combining generation with battery and thermal storage and intelligent controls.

A crucial element of the active building approach, which we have been developing at Swansea University's SPECIFIC Innovation and Knowledge Centre, is performance evaluation: data is collected and analysed to detect and resolve faults quickly, optimise systems, and develop predictive control strategies and planned maintenance regimes.

A critical feature of the active buildings is that energy data is collected continuously and used to improve performance; for instance, we saved 1MWh in the second year of operating our Active Office compared to the first. This was only possible due to data collection, which enabled us to detect faults and sources of unexpectedly high energy usage that we were then able to rectify.

While LEED, BREEAM and other measurement systems are a good way of getting people to think along the right lines, they do not in themselves guarantee efficient or low-energy buildings unless there is also proper building performance evaluation. Buildings should therefore be monitored for at least two or three years after construction in order to prove their energy performance.

To date, SPECIFIC has focused efforts on honing this concept on new-build demonstrators at Swansea University's Bay Campus. However, the concept could be applied equally well to existing buildings, albeit with a few more challenges.

A building's current performance should be understood by undertaking energy monitoring and thermographic surveys, for example, before determining the most appropriate retrofits. Factors such as heritage status, adjacent buildings, land and urban environment, orientation, fabric and energy consumption must all be considered as well, with buildings assessed according to their particular circumstances.

We need for instance to embed energy flexibility in the buildings we are creating. This means equipping properties with storage and controls that enable building management systems to import or export energy at the optimum moment, according to carbon intensity, cost, or time of day.

Using energy storage and smart controls, an active building is able to control its interactions with the grid. For example, it will export its own renewably generated energy when it recognises demand on the grid is high and carbon-intense – as indicated by the National Grid ESO site – and draw on the grid when demand and carbon intensity are both low. This will ensure the building only uses the lowest-carbon energy and does not stress the grid.

Renewable energy is just part of the solution. Without energy storage and smart control strategies, exports to the grid are uncontrollable and sporadic due to climatic conditions and the infrastructure was not designed to accommodate this fluctuating energy supply. To ensure a stable electricity supply we need flexible energy strategies, and the active building concept offers just that.

The benefits of this include ensuring that the buildings we construct now will not need retrofitting in the future. Owners should see lower fuel bills, and will be helped in meeting their zero-carbon objectives – which is particularly important for companies and large estate owners.

Investors and portfolio owners will meanwhile find active buildings are more attractive to tenants because of their low-carbon and low-energy features. Portfolio owners such as housing associations, university estates, government departments and health boards will also be able to see clearly how their buildings are performing and identify any areas for improvement.

One benefit of having demonstrator buildings is that we can prove the safety and reliability of innovative technology before it is deployed more widely. There are many different technologies that could be used in an active building, and at SPECIFIC we enjoy trialling as many as we can.

We focus on solar energy and amongst many other research groups we have one investigating the next generation of printable photovoltaics. But we are also open to any technology that can help achieve our energy and carbon reduction targets.

To enable others to adopt the active building concept in their own projects, we have also developed a toolkit that includes detailed case studies and suggested technologies.

The building with the lowest embodied carbon is one that already exists, as the carbon involved in its construction will already have been emitted. According to the UK Green Building Council, in the UK, 80% of the buildings that we’ll be using in 2050 – the date of our net-zero carbon target – are already in existence. So there is an urgent need to find ways of upgrading existing building stock.

While we have started with new builds at SPECIFIC, the active building concept can equally well be applied to existing stock. However, we recognise that different measures will be appropriate to different building types.

For example, we are demonstrating technologies on a 1990s industrial warehouse building in Margam, south Wales, which has been retrofitted with a transpired solar collector connected to a diurnal thermal storage system to provide indoor space heating, a test rig to investigate different types of solar thermal and photovoltaic systems, and a novel interseasonal thermal storage system that would allow the use of summer heat in winter.

As with the new buildings, the warehouse enables us to trial technologies in a relatively risk-free setting and gather data to inform others, developing an understanding and practical experience of the options for the future. Figures on its performance are currently being analysed and will be published before too long.

We must approach retrofit projects with caution and learn from past mistakes, and our demonstrators can provide valuable insights on this. Green finance has often led to inappropriate and poorly executed retrofits in the past, with some devasting consequences for buildings and their occupants. There is no uniform approach, though, and any retrofit scheme must be accompanied by appropriate upskilling for designers and installers.

In September 2020, the UK government announced £3bn of funding for retrofit projects, comprising £2bn for housing through the Green Homes Grant (GHG) scheme, and £1bn for publicly owned buildings through the Public Sector Decarbonisation Scheme. It is anticipated that the GHG will enable 600,000 homes to improve their energy efficiency and reduce their carbon emissions. Adopting a considered approach, where current building energy performance is considered and assessed first, will help ensure this approach is successful.

A particular challenge for Wales is retrofitting buildings dating from before 1919, which, according to BRE Trust, make up 26% of all existing homes. This is not just a problem in terms of operational carbon – 10% of households in England and almost a quarter in Wales are in fuel poverty, spending more than 10% of their income on fuel.

While the Green Homes Grant is available in England, the Welsh government launched its optimised retrofit programme in November 2020, which will provide £19.5m in funding to test new approaches for decarbonising existing homes.

Under this scheme, a project led by the Sero Group with 68 partners – including SPECIFIC spin-out the Active Building Centre Research Programme – will develop ways to enable retrofit of around 1,370 homes. This will act as a pathfinder for further retrofits across the country.

Meanwhile, the Low-Carbon Built Environment group at Cardiff University is undertaking retrofits in Wales, combining energy monitoring data with existing fabric performance and climate data to model the most cost-effective and energy-saving measures for housing.

Social housing association Pobl also recently started work on one of UK's largest energy retrofit schemes in collaboration with Sero. This involves installing energy storage and smart energy management systems in 650 homes in Swansea. The homes will be fitted with photovoltaic panels, battery storage, smart thermostats and intelligent heating controls as well.

Other retrofit schemes under way throughout the UK include several pilots of the Dutch Energiesprong approach, a method that involves a whole-house retrofit with prefabricated, insulated roof and wall panels, solar PV and smart heating, ventilation and cooling systems in a single package that is neatly fitted over an existing dwelling, like a blanket.

Recognising the diversity in our existing building stock and the need for a considered approach to retrofit is essential in successfully decarbonising homes and other buildings. It is, however, important to recognise that many existing buildings will be challenging to retrofit due to their heritage status, planning restrictions, form and costs.

Installing a robust data monitoring system – and perhaps considering energy storage – will allow such buildings to make best use of low-carbon electricity supplied by the national grid if smart control strategies are implemented.

Transport and electric vehicle charging are important aspects of the active building approach. We advocate provision of smart electric vehicle charging, which plays a part in controlling energy flows between a building and the grid, either using electric vehicles as additional energy storage devices, or as energy sources at times of high peak energy demand.

SPECIFIC has recently been working with Transport for Wales to develop an Active Rail Shelter prototype at SPECIFIC’s site in Margam, south Wales. This would provide lit shelters with information displays powered by a photovoltaic roof at remote stations along the Welsh rail network.

The Active Office has hosted a trial demand-side response project with Evergreen Smart Power and other partners, which shows how a building can act as a virtual power plant in a flexible and responsive system.

Related competencies include: Construction technology and environmental services, Sustainability