Every building is designed twice. Once on paper, where it performs beautifully — efficient, balanced, comfortable, hitting every target the design team modelled. And once in reality, where it does something rather different. The distance between those two buildings has a name in our industry: the performance gap. It is one of the most persistent and least confronted facts about the built environment, and the coming years are going to make it impossible to ignore.
The gap is not a sign of bad design. It is a sign that buildings are living systems, not finished products. The moment a building is handed over, it begins to drift. Occupancy patterns change. Tenants reconfigure space. Control settings get nudged to silence a complaint and never nudged back. Sensors fail quietly. Plant ages. Each individual change is small and reasonable; collectively they pull the building away from the way it was meant to run, and the energy penalty compounds year on year. A building commissioned to perform at design intent in January will, left alone, perform measurably worse by the following January — and worse again the year after.
The regulator is about to start measuring what actually happens
For years this drift has been invisible to the official record, because the official record was modelled, not measured. An EPC has historically described how a building should perform under standard assumptions — a useful proxy, but a proxy nonetheless, and one that says nothing about whether the building delivers on those assumptions in operation.
That is changing. The EPC framework is being reformed, with the basis of assessment moving toward how buildings actually behave — how they retain heat and perform in use — rather than relying solely on modelled inputs. This is a profound shift, and the industry has not fully absorbed its implications. When the metric that governs lettability moves from designed performance to measured performance, the performance gap stops being an academic curiosity and becomes a direct commercial liability. The drift you cannot see is the drift that will eventually show up on the certificate that determines whether you can let the space.
This reframes what good asset management even means. It is no longer enough to procure an efficient building and assume the efficiency persists. Performance has to be treated the way a portfolio is treated — as something monitored continuously and steered actively, not set once and left.
You cannot manage what you cannot see — and you should own what you can
All of this depends on one thing the industry has been remarkably casual about: data. You cannot close a performance gap you cannot measure. You cannot tell whether a building is drifting if you are looking at an annual bill rather than the live behaviour of its systems. Continuous insight into how a building consumes energy — granular, current, and trustworthy — is the precondition for managing it at all. Without it, every decision is a guess dressed up as a judgement.
Which raises a question owners ask far too late: who actually owns that data? In too many buildings the operational data is fragmented across the systems that generate it, locked in proprietary formats, or effectively held by whoever installed the controls. That is a strategic weakness. The data describing how your asset performs is, increasingly, part of the asset’s value — it is the evidence base for compliance, for valuation, for every future decision about where to spend. It should sit with the owner, in a single trustworthy source of truth, not scattered across vendors who have no particular incentive to surrender it.
The mental model that follows from all this is simple but unfamiliar. Stop thinking of a building as an object you complete and then own. Start thinking of it as a process you run — one that requires measurement, attention and continuous correction to stay on course, exactly like any other system whose performance matters and decays without it.
The owners who thrive through the next decade of tightening standards will not necessarily be the ones with the newest plant or the deepest retrofit budgets. They will be the ones who can see, in real numbers, what their buildings are doing right now — and who can steer them back on track before drift becomes a discount. Measurement is not the paperwork of decarbonisation. It is the whole game.
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