Retrofitting old builds: How the GDST is implementing a vision for decarbonisation across its education estate

There was keen interest in how The Department of Education’s Sustainability and Climate Strategy would help deliver the ambitious Net Zero targets in the education estate: state Primary and Secondary Schools account for 25% of energy use in the wider public sector. There is therefore large potential for savings and contribution toward the overarching Net Zero target.

So how did the DfE propose to decarbonise the education estate?

The Strategy sets out that from 2023 all new school buildings delivered by DfE will be Net Zero in operation. London Energy Transformation Initiative’s (LETI) Climate Emergency design guide shows how this can be achieved: a new building with net zero operational carbon does not burn fossil fuels, is 100% powered by renewable energy and is designed to demand the least amount of energy for heating, lighting, and other services.

Designing and building low and zero carbon new buildings is critical to delivering the UK’s Net Zero strategy and it takes clever engineering and forward-thinking designers to do that. But it still is, arguably, not the building sector’s biggest challenge. That position is reserved for the elephant in room: the existing building stock.

Extending the life of existing buildings is more sustainable in terms of resource efficiency, while a statistic from the residential sector reveals that 80% of buildings that will exist in 2050 have already been built. That percentage will be even higher for the education estate – less schools are built than homes every year. The majority of schools that will exist in 2050 are already constructed.

Opportunity and challenge

So, in retrofitting this existing stock lies the biggest opportunity – and the biggest challenge.

To retrofit a building means to upgrade it, so that it can respond to the need to reduce its energy use, while improving the internal environment and health of the occupants.

How is that achieved? A series of steps can be taken, including replacing windows and doors, adding insulation to roofs, walls and floors, using energy efficient lights or adding renewable energy generation, such as photovoltaic panels. In recent years, because the electricity in the UK has become cleaner in terms of its carbon content, another way to help reduce the carbon footprint of buildings is ditching gas boilers for electrical heating, such as heat pumps.

This is not easy in practice. The challenges of delivering these improvements have been long known in the industry and are multi-dimensional: not only they are investment-heavy and require careful planning and delivery, but they come with technical complications.

Historic or listed buildings will have constraints on how much designers can interfere with the fabric: during work on GDST’s Brighton High Temple Building, a Grade II listed building, built in 1819 (Figure 1), works to improve windows and the fabric’s thermal performance had to be carefully balanced with enhancing and preserving the heritage assets. Structural and load constraints may limit how many solar panels can be installed on a roof, while condensation and mould can be the result of cold spots if insulation is not applied correctly.

Engineers and designers have been working for years on ways to get around these issues. With careful planning and delivery, bespoke solutions and monitoring, it has become possible to overcome or manage these challenges and deliver energy savings.

To the long list of demands for a successful retrofit, the electrification trend has added some more: getting rid of gas boilers in favour of a heat pump for example, involves more than a simple replacement. Buildings should be well-insulated and have ideally larger radiators that can work well with the lower temperatures that a heat pump will deliver. Space needs to be found, and acoustic measures must be taken, both of which can be sensitive in a school environment.

Electrical infrastructure should also be resilient to accommodate the change. Ensuring that these new systems can be properly maintained and operated is also critical for the success of the electrification trend. It also helps with managing operating costs, since electricity is more expensive than gas.

… the reality is that retrofitting the existing building stock requires planning, skills, investment, and constant re-calibration

Design teams and technology specialist are accustomed to these challenges, and they are constantly coming up with ways to overcome and get ahead of these. But the reality is that retrofitting the existing building stock requires planning, skills, investment, and constant re-calibration from monitoring of existing installations and lessons learned.

This is not to undermine the level of ambition behind the DfE’s Zero Carbon target for new buildings, and the potential to create substantial momentum in the construction industry.

Passive design considerations

At GDST, we are also thinking hard about the carbon footprint of our new buildings. Proposals for our new Junior School at Notting Hill and Ealing (Figure 2 – main image) employ principles of passive design to reduce the amount of energy the building will need to operate: a super insulated fabric and airtight construction will minimise the amount of heat lost to the environment. Carefully designed glazing will balance solar gains and overheating during the summer months, with daylight, to help reduce electricity needed for artificial lighting.

… heating will be delivered via air source heat pumps, powered by electricity

There will be no gas supply to the building and heating will be delivered via air source heat pumps, powered by electricity. At GDST we are now procuring 100% renewable electricity, which helps reduce the carbon footprint associated with electrical demand in schools. Finally, the building design incorporates south-facing slopes on the sawtooth roof that will be used to mount solar panels that produce renewable electricity.

Getting on with urgent retrofitting and committing to all new school buildings being Net Zero in operation will ensure that, as a sector, we learn and develop the necessary skills needed to deliver this at scale and on time. This is the only way our buildings will be part of the solution and not the problem; and help inspire their occupants to do the same.

Main image – Fig 2. NHE new Junior School – proposals include a series of sustainability measures. Image credit: Skelly & Couch