The revision of EN 16798-17 officially started in February 2026. This new revision is closely linked to one of the major evolutions introduced by the recast Energy Performance of Buildings Directive (EPBD): the strengthening of requirements related to ventilation inspection and indoor environmental quality (IEQ).

The revision therefore comes at a pivotal moment. Buildings are becoming increasingly energy efficient and increasingly smart, while at the same time expectations regarding indoor air quality (IAQ) continue to grow. In this context, traditional inspection approaches based only on visual checks and occasional airflow measurements are no longer sufficient.

Furthermore, field observations suggest that fewer than half of ventilation systems operate as originally intended, which seriously undermines the credibility of relying on installed systems alone to ensure indoor air quality, since even a well-designed ventilation system cannot deliver acceptable IAQ if it is not correctly commissioned, verified and regularly inspected; promoting ventilation systems must therefore go hand in hand with promoting systematic and relevant inspection throughout their operational life.

The future EN 16798-17 aims to provide a modern framework capable of assessing the real performance of ventilation systems, including smart, demand-controlled, hybrid and natural ventilation systems.

Why is EN 16798-17 being revised?

EN 16798-17 was first published in 2017 to support Member States in implementing the previous EPBD requirements regarding the inspection of air-conditioning and ventilation systems. The standard mainly focused on inspection methodologies from an energy perspective, while also addressing some indoor climate issues linked to ventilation systems.

The publication of the new EPBD in 2024 significantly changed the landscape.

The new directive now requires Member States to ensure regular inspection of ventilation systems in certain large buildings every three or five years, depending on the type of system and building. However, the EPBD also introduces an important alternative: inspections may be simplified when buildings are equipped with proper monitoring functionalities of IEQ.

Another major novelty of the EPBD is the explicit requirement to consider indoor environmental quality together with energy performance. This is particularly important for ventilation systems, which directly influence the level of pollutants (inc. particles), CO₂, humidity and the thermal comfort.

As a consequence, the revision of EN 16798-17 must now address several new challenges:

• How to inspect increasingly smart and demand-controlled ventilation systems (with no constant flowrate);
• How to assess the actual performance of ventilation systems rather than only their design intent;
• How monitoring may simplify inspections;
• How to integrate IAQ considerations into inspection procedures.

From visual checks to measured performance

One of the main evolutions currently discussed within CEN TC156/WG23 is the introduction of mandatory measurements during ventilation inspections. Historically, inspections mainly relied on visual checks, document verification and occasional airflow measurements, which was generally sufficient for conventional constant-air-volume systems. However, ventilation technologies have evolved rapidly. Demand-controlled, hybrid and natural ventilation systems now continuously adapt their operation according to occupancy, CO₂ levels, humidity, pressure or weather conditions. In such systems, a simple airflow measurement at a given moment is no longer enough to assess whether the system actually performs as intended.

The revision of EN 16798-17 therefore aims to introduce more operational and performance-oriented inspection approaches. Depending on the type of system and its design philosophy, inspections could include airflow or proxy measurements, verification of control strategies, assessment of IAQ indicators, energy use analysis and consistency checks between monitored data and expected system behaviour. While the objective is not to impose heavy measurement campaigns in all buildings, the principle emerging from the discussions is that inspections should increasingly rely on objective operational evidence rather than only visual observations.

The discussions within CEN TC156/WG23 currently explore several complementary approaches.

IAQ monitoring and the link with EN 16798-1

The possibility to assess ventilation performance partly through indoor air quality measurements is currently discussed in the revision of EN 16798-17. If a building continuously demonstrates acceptable IAQ conditions, this could provide strong evidence that the ventilation system performs correctly. This aligns closely with the philosophy of the new EPBD, which allows simplified inspections or exemptions when adequate monitoring is implemented.

However, using IAQ measurements as an inspection tool raises an important challenge: defining what “acceptable IAQ” actually means. Today, European countries still rely on very different indicators, thresholds and assessment methodologies. Some mainly use CO₂ concentration, while others also include particles, humidity, VOCs or formaldehyde, etc., often with different averaging methods and limit values. Without clearer and more harmonised IAQ criteria, it remains difficult to use IAQ measurements as a robust basis for inspection.

This is where the parallel revision of EN 16798-1 becomes particularly important. The revised standard is expected to provide methodologies helping national decision-makers define relevant IAQ indicators, threshold values, performance categories and assessment methods. It should also introduce a more performance-based approach focused on the actual indoor environmental conditions achieved in buildings rather than only on design airflow rates. The alignment between EN 16798-1 and EN 16798-17 will therefore be essential: EN 16798-1 would define what constitutes acceptable IEQ performance, while EN 16798-17 would define how inspectors can verify that ventilation systems effectively deliver this performance in operation.

Towards a new generation of ventilation inspection

Ventilation systems are becoming increasingly smart, connected and adaptive, with growing use of demand-controlled, hybrid and natural ventilation strategies in both residential and non-residential buildings. At the same time, expectations regarding indoor air quality, health and operational energy performance continue to rise. Inspection methodologies must therefore evolve accordingly. The revised standard aims to provide more robust and operational approaches adapted to these new systems, including clearer guidance on measurements and monitored data, while remaining focused on regular inspections during operation rather than handing-over procedures (already covered by EN 12599 and EN 14134). The revision works officially started in February 2026 within CEN TC156/WG23 and is expected to continue over the coming years, with a first draft of EN 16798-17 hoped for by the end of 2028 and a first draft of the revised version of EN 16798-1 potentially available around 2027. Although discussions are still at an early stage, one conclusion is already clear: ventilation inspection is undergoing a significant transformation in which measurements, operational evidence and indoor environmental quality shall play a central role.

Article by Valérie Leprince, Cerema, France