New schools must be Net Zero in operation, and refurbishments must demonstrate significant emissions reductions. Our multidisciplinary team offers a step-by-step guide to meeting the Department for Education’s new output specification, and balancing cost and carbon.

The government has announced welcome investment in the UK’s school buildings – but it comes with some ambitious carbon targets, as the public sector leads the way to Net Zero Carbon by 2050.  

Under the latest output specification from the Department for Education, new schools must be Net Zero in operation. This means they do not burn any fossil fuels, can be powered by 100% renewable energy, and use that energy very efficiently.  

Refurbished schools will also have to demonstrate a significant improvement in energy performance.  

For most schools, this will be a big leap – so how can they get there?  

1. Starting with the building fabric

Whether it’s a newbuild or a refurbishment, the Department for Education specification takes a “fabric-first” approach.  

“This means going as far as you can with thermal insulation, double or triple-glazing and airtightness to make the fabric of the building as efficient as possible,” says Pete Langford, a Partner and MEP Cost Manager at Ridge, who has worked on many school projects. “There are limits on how much schools can spend per square metre, so it’s about getting a balance between upfront cost, and running costs and carbon savings.” 

To help schools do this, the DfE has also set mandatory “energy use intensity” targets for new buildings: the maximum kilowatt hours per square metre required by uses such as lighting, heating and IT.  

There is a similar approach for retrofits, but it’s more flexible, says Kat Adair, Senior Associate in the Sustainability team at Ridge. “It’s still focusing on energy, but instead of having a fixed target, it’s about improving performance compared to the original building. Essentially, we build a digital twin of the existing school in our energy modelling software to show how it’s currently operating, and then we have to show we are making improvements to that baseline.”  

Essentially, we build a digital twin of the existing school in our energy modelling software to show how it’s currently operating, and then we have to show we are making improvements to that baseline.”  

This approach is called the “energy hierarchy”, she explains. “First, we maximise the efficiency of the building fabric to reduce the energy needed to run it, before providing that energy in a low-carbon way. Adding renewables like solar photovoltaics is the very last step, when you’ve done everything else.” 

2. Switching from gas to electricity

The next step is to install a low-carbon source of heating – typically an air-source heat pump. Heat pumps operate like a fridge in reverse, extracting warmth from the air. This is very efficient, particularly at around 50°C. But there’s a catch: “The UK’s energy market has yet to catch up with its Net Zero aspirations,” says Phil Kelly, Net Zero and Circularity lead at Ridge. “Today, electricity is four times more expensive than gas, which means that an overnight switch could result in higher bills – unless the heat pump can operate four times more efficiently. That’s a big ask.”  

This is on top of the capital investment. As a relatively new technology in the UK, an air-source heat pump is more expensive than a gas boiler, though the cost is coming down.  

“In the majority of cases, it’s not viable to switch all buildings from gas to electricity in one go, or without additional interventions,” says Phil. “But we can set out a phased approach, with hybrid solutions along the way, to steadily reduce carbon and work towards the ultimate goal of Net Zero.” This begins with an options appraisal that looks at the cost, potential savings and carbon impacts of a whole range of interventions, as well as any wider benefits. Then, we identify the interdependencies between them. For example, the more we can improve the fabric of the school building, the smaller the heat pump required to serve it, and the less need for invasive upgrades to pipework and radiators.  

One alternative to a heat pump is a direct electric boiler, which is cheap to install and the quickest way to decarbonise, as an overnight swap from fossil fuels to electricity that can be generated from renewable sources. Again, this means much higher bills because of the unit price differential, says Pete. “But it could work on a very small scale, for example on a countryside primary school with a 50kW boiler. While the increase in bills would be significant, it’s an increase in a much smaller bill to start with. So if it was £25,000 a year, it might be £35,000. Unfortunately, decarbonising a school doesn’t always mean lower energy bills, but there are measures we can take to reduce the costs.” 

3. Reducing bills with renewables

This is where renewables like solar photovoltaics come in. By generating electricity on site, schools can reduce the amount they need to buy from the grid.  

“That can be a really easy win in terms of reducing the energy bill, especially as schools often have a reasonable amount of roof area,” says Kat.  

The cost of installing solar panels has plummeted over the last decade, and their efficiency has improved, so that the initial investment is quickly justified by the operational savings. “The payback might be as short as seven years, depending on the specifics of your site. For a building like a school that’s going to be there a lot longer, it’s almost a no-brainer when it can save so much money over the long term.” 

The cost of installing solar panels has plummeted over the last decade, and their efficiency has improved, so that the initial investment is quickly justified by the operational savings.

Visible measures like solar panels can also be a good learning tool for students, she adds.  

4. Learning from post-occupancy evaluations

Net Zero is a behaviour change too. So we also need to look beyond the building itself, to how it is used.  

There are simple measures to reduce energy bills in both existing and new schools. “It’s things like making sure the people using the building know how to operate it. We can put in a fancy new building services design or automated controls, but if teachers and students don’t understand it, they’re not going to get the value out of it,” says Kat. “That soft-landings approach is really important. It doesn’t have to be the most high-tech solution to be the most effective.”  

There will also be useful lessons from previous projects. The DfE framework has also strengthened the requirement for post-occupancy evaluations, which look at actual energy use to determine whether a building is performing as anticipated in its first 12 months.  

“Our modelling is never going to be exactly the same but there are too many variables in how people use buildings day to day, but if we can take the knowledge that we gain from those exercises into the next project, that’s going to help reduce that performance gap every time,” says Kat. “Over the next few years, there will hopefully be some really good data coming out of those.” 

For example, while completely sealed, mechanically ventilated schools might perform better on paper, feedback from occupants is that they prefer having some control over their environment. “If people can open a window or adjust a thermostat, the range of temperatures that they’re comfortable with increases by a couple of degrees. They’re more tolerant of a hotter or colder environment when they have control over it. That two-way communication is really important, and it comes through really strongly when you do post-occupancy evaluations.” 

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Phil Kelly is Net Zero and Circularity lead at Ridge. You can contact Phil on philkelly@ridge.co.uk

Kat Adair is Senior Associate in the Sustainability team at Ridge. You can contact Kat on katadair@ridge.co.uk. 

Pete Langford is a Partner in our MEP Cost Management team. You can contact Pete at petelangford@ridge.co.uk