The DfE frames the energy side of net zero for schools as a simple hierarchy: Be Lean, Be Clean, Be Green, Be Seen.
It is a sensible order of priorities, and it is worth understanding, particularly the part that is easy to misread for an existing building.
Be Lean means using less energy in the first place, through efficient equipment, good controls and a fabric-first approach. Be Clean means meeting the remaining demand efficiently and moving off fossil fuel onto low-carbon heat. Be Green means generating what you can from on-site renewables. Be Seen means metering, monitoring and reporting, so performance is tracked and improved rather than assumed.
Here is the part that trips people up. The DfE’s headline energy targets, around 52 kWh per square metre for a new primary and 67 for a new secondary, are written for new buildings. They are a demanding standard that a well-designed new school should meet. They are not a fair test for an existing Victorian or 1970s building, and holding an existing school to them simply produces a fail that tells you nothing. For existing schools, the honest approach is to benchmark against real operational data, using the school’s Display Energy Certificate and the CIBSE operational benchmarks, and to treat the new-build figure as a direction of travel rather than a pass or fail.
So how should an existing school read its position? Start with the DEC rating, which is the recognised operational measure. Then look at energy intensity against the benchmarks, and crucially look at electricity and heat separately, because a school can have efficient electrics and still carry a heavy gas load. Look at how dependent the site is on fossil fuel, whether there is any on-site renewable generation, and whether energy is actually being metered and monitored.
For most existing schools, the single biggest lever sits under Be Clean: heat. Most schools are heated by gas, and heat is where the majority of emissions live. This has become clearer over the past year, because grid electricity has now fallen below natural gas per unit of energy, which means replacing a gas boiler with an efficient heat pump genuinely reduces carbon rather than moving it around. Fabric improvements usually come first or alongside, so the heat pump can be sized efficiently, and renewables follow once demand has been minimised.
The message is not complicated. Know your baseline, benchmark honestly against operational data rather than a new-build standard, and put the effort into heat. That is where the carbon is, and it is where the DfE route points.
How Nero can help
We assess existing schools and trusts against this framework, benchmark them against the right operational data, and set out a prioritised route with the biggest carbon levers first.
To find out where your biggest savings sit, get in touch
