At a breakfast briefing last month, Sarah Ratcliffe, CEO of the Better Buildings Partnership (BBP), showed a slide depicting a very strange situation – but one which she found not the least bit surprising.

Lem Bingley

PW editor, Lem Bingley

Let me back up. Every year, the BBP gathers data on real-world energy use from across its membership of 50-odd major building owners. This year’s study covered 1,275 properties amounting to 135m sq ft.

Plotting actual energy used (per square foot per year) against each building’s rating under the Energy Performance Certificate (EPC) system leads to a very odd result. You might imagine a steadily rising graph with low energy usage for buildings ranked ‘A’ and ‘B’ and much higher consumption at the other end of the EPC scale. What you actually see is chaos – a very wide variation in the energy gobbled up, seemingly irrespective of rating.

“EPCs are not a good indicator of performance in use,” Ratcliffe observed, with some understatement.

Her lack of surprise is because the finding is nothing new. Eleven years ago, BBP and agency JLL published a report comparing measured energy use of two government buildings, one rated ‘B’ and one rated ‘E’. The results were topsy-turvy. “There is little or no correlation between EPC ratings and actual energy performance,” the 2012 study concluded, in very large lettering.

So why are we still bothering with EPCs, if they are such an unreliable indicator of performance? Because they are enshrined in regulation, of course.

Ratcliffe also highlighted data from Climate Change Committee reports showing emissions from commercial buildings in the UK have “flat-lined” for more than a decade – a period in which many BBP-tracked buildings have achieved steady year-on-year improvements.

“If those BBP member buildings can improve their energy efficiency, why is that not coming through for the rest of the sector?” she asked. “The reason is that in the UK, we have a compliance-based approach to energy efficiency.”

This is why BBP is backing NABERS as a more accurate way to assess sustainability. Unlike EPCs, NABERS ratings are assessed annually. And as NABERS director Carlos Flores told the breakfast meeting: “The only way to get a better rating is to use less energy.”

NABERS was developed in Australia, where Flores said the average improvement had been 33% less energy use – across the whole market, not just the top-rated buildings – since NABERS disclosure was made mandatory in 2010.

It is high time that the UK followed suit – if not with NABERS, then with another performance-based, rather than check-box, measure. NABERS is not the only option.

This is a topic we explore further this week in our Get Set for Net Zero campaign, in an interview with Katherine Beisler of consultancy Hollis.

Hollis is a lead partner in our campaign, alongside fellow lead partner Deepki, founding partner Mishcon de Reya, supporting partner Octopus Real Estate and knowledge partner UKGBC.

I’m grateful to all five of our backers for helping Property Week to spread the message. The purpose of the Get Set for Net Zero campaign is to discuss how the property industry can reduce its emissions to zero in the real world, not just on paper or in theory.

I hope you will join us on the journey.