homenews and insights introducing iso 52120

Was there ever a more important time to decarbonise and improve energy efficiency? Introducing ISO 52120

By Dr Andrew Eaton
01 September 2022

Product Marketing Manager

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With the double hit of the climate crisis and rising energy costs, it has never been more important to achieve the best possible energy efficiency. However, this does not always mean capital investment in new plant. Research has shown that savings of typically 30% can be achieved by managing your BEMS strategy at optimum.

Many organisations are unaware that there is an international Standard for BEMS control systems. It is specifically designed to review BEMS performance and strategy, and the influence it has on a building’s energy consumption by comparing a building's BEMS against the best practices as described in the Standard. It was created by the European (CEN TC 247) committee1 and has been independently verified by the Technical University of Dresden. Like the energy efficiency rating on your refrigerator, this standard divides BMS systems into efficiency classes, in this case from A to D.

Energy efficiency Class C is the baseline for buildings with a BEMS2. Buildings in which the BEMS is not operating efficiently are rated as Class D, and typically use 50% more energy than Class C.

Alarmingly, the European Commission has found that 75% of buildings in the EU and UK are rated as Class D3.

However, it can get better. Through extensive research, it has been shown that a demand-led, rather than a timeclock-based strategy, such as is described in Class A of the Standard, can result in an energy-use reduction of 30%. Two things have occurred recently which will significantly increase the awareness, and adoption, of this Standard.


The standard was originally developed in Europe and adopted in the UK as BS EN 15232:2012, “Energy performance of buildings. Impact of Building Automation, Controls and Building Management”. This was essentially a European Standard that was adopted in the UK by British Standards (BS). However, in December 2021, it was adopted, virtually unchanged, by the International Standards Organisation (ISO) as international Standard ISO 52120-1:20214.

This status is likely to make it more accessible and encourage greater adoption.

Building Regulations 2010: 2021 edition Part L, Conservation of Fuel and Power

On 15th May 2022, the Building Regulations in England changed to require buildings to achieve a significantly greater level of energy efficiency.

6.72 A building automation and control system installed in a new or existing building, where the building meets the space heating or cooling criteria in paragraphs 6.66 and 6.67, should be capable of carrying out all of the following functions.

a. Fully complies with BS EN ISO 16484 6.

b. Continuously monitors, logs, analyses and allows for adjusting energy use.

c. Benchmarks the building’s energy efficiency, detects losses in efficiency of heating, ventilation and air conditioning systems, and informs the person responsible for the facilities or building management about opportunities for energy efficiency improvement.

d. Allows communication with connected fixed building services and other appliances inside the building and is interoperable with fixed building services across different types of proprietary technologies, devices and manufacturers.

A BS EN 15232 Class A rated type system would meet these requirements.

It should be noted that :

  • Whilst these Regulations currently apply to England only, the devolved governments in the other UK countries are expected to adopt them.
  • This version of the Regulations was in development before the publication of ISO 52120 and is expected to be updated in a future revision

Whilst not explicitly specified in the Regulations that EN 15232 Class A must be applied, it does state that applying EN 15232 (or ISO 52120) would prove that the regulations have been met.

To achieve a Class A rating a demand-based strategy needs to be applied. This means that rather than have HVAC, such as boilers, come into operation at set times, they would only come into operation if a particular room or zone is occupied. This requires, amongst other things, the inclusion of occupancy sensors. Whilst this increases the initial cost of a new build or refurbishment, it will result in significant savings over the lifetime of the building, which far outweighs the initial investment Often, however, such energy savings are cut from the design, through a process of Value Engineering . As a result, building owners/occupiers discover that their buildings are not as energy efficient as was specified, and thus face higher energy costs than expected.

The Investopedia website definition of VE7 includes the statement:

Value engineering promotes the substitution of materials and methods with less expensive alternatives, without sacrificing functionality.

Clearly, the lack of energy efficiency does, represent a sacrifice of functionality and so more specific instructions in the specifications need to be applied and the new Building Regulations described above should facilitate this. By specifying that the building should conform to EN 15232 Class A, it will make it harder to VE out the equipment necessary to achieve this. It cannot be argued that the sensors are not required because the requirement to achieve EN 15232 Class A demands them. The inclusion of a variant of the following sentence in the specifications may help:

Building must achieve EN 15232 class A to demonstrate compliance with Building Regulations 2010: 2021 edition Part L, Conservation of Fuel and Power.

SSE Energy Solutions can help

SSE can advise on both the development of specifications to achieve the Standard and can conduct a survey of your buildings to both assess your current ISO 52120 rating and advise on measures to improve it.