Subprime office stock faces the risk of becoming stranded not just because of poor energy performance, but because of poor measurement.
As policy pressure ramps up through the Minimum Energy Efficiency Standards (MEES), which seeks to improve energy performance certificate (EPC) ratings, landlords and developers are scrambling to comply.
But compliance alone doesn’t equal performance. EPCs remain a design-based model, unable to reflect how a building actually operates once tenants move in.
That’s why we are calling for a smarter approach: performance-based metrics that reflect reality, not just intent.
Tools such as NABERS UK offer a credible, trusted way to benchmark actual energy use and the gap between design and delivery. Yet uptake in the secondary office market remains low. To unlock progress, we propose a targeted rollout of pilot retrofit projects using NABERS UK in subprime buildings, backed by funding and visibility. These pilots would build market confidence, generate replicable models and set a new standard for energy accountability.
As Liz Grove, head of sustainability at Greengage Environmental, explained:
“There is plenty of evidence to show that EPC ratings are not a good measure for how efficient buildings are, with virtually no correlation between EPC rating and actual energy use. This is because the EPC calculation methodology is based on simplified, standardised modelling which provides a theoretical performance that do not reflect how the building will be operated.
It is important to use metrics that focus on actual energy performance in operation to ensure energy efficiency interventions deliver real operational improvements. NABERS UK, which is based on 12 months of metered energy data, provides a better benchmark to assess how efficient an office building actually is.
NABERS also incentivises the ongoing performance optimisation of office buildings in operation, ensuring the desired performance is not only achieved upon completion of the project, but maintained, and in many cases improved, during the operational life of the building.”
This is not just about operational transparency – it is about aligning metrics with what tenants actually care about: thermal comfort, building usability, running costs and climate performance. Tomorrow’s occupiers will demand proof, not promises.
Ken Watson, workplace manager at Mitsubishi Corporation, London Branch, noted the significance of landlords engaging with and bringing their customers along on the journey:
“Occupiers appreciate that there’s a cost to driving changes and making buildings sustainable so it’s about working with landlords (and the other tenants within the space) and coming together to achieve results that we all want in the longer term. It’s a two-way street – you may ask a landlord ‘What’s your plan and how will you support us?’ and landlords should be countering that with ‘And what can we do to help you?’ – it’s an ongoing process, with information sharing being a crucial piece of the jigsaw.”
By funding pilot programs and incentivising performance-based disclosure, the UK real estate sector can shift away from box-ticking and toward real operational improvement – ensuring that subprime offices are not dismissed based on outdated or misleading metrics.
It’s time to measure what matters.
