EN ISO 52120-1 is the standard that measures the contribution of building automation to energy performance. It evaluates how the building is operated, not the thickness of insulation or boiler efficiency. It replaces EN 15232-1:2017
How is the class determined?
Based on the sum of control functions actually installed in the building. Seven areas are evaluated: heating, domestic hot water, cooling, ventilation and air conditioning, lighting, shading, and technical building management (TBM). Each function is rated individually from D to A.
A — High energy performance BACS + TBM, demand-based operation
B — Advanced BACS + TBM
C — Standard BACS, reference base
D — Non energy efficient BACS, modernization required
Factors for office buildings
Using Class C as reference, thermal energy / electricity:
A: 0.70 / 0.87 — B: 0.80 / 0.93 — C: 1.00 / 1.00 — D: 1.51 / 1.10
In other words, a Class D office building consumes more than twice the thermal energy of a Class A office. Approximately 75% of the building stock in the European Union and the UK is rated as Class D.
The class is not a score, but a lower bound. A building is assigned to Class X if all implemented functions are at least Class X. Scores are not summed up — the worst function determines the class. In a building where fourteen functions are at A level, if a single function remains at D, the building is Class D.
Therefore, the most valuable output is not the class letter, but which function is keeping you there. You don't need to renew the entire system to jump a class; you only need to upgrade those binding functions.
15 questions, approximately 3 minutes.