For decades, building performance in Europe was judged mainly on energy. Indoor air quality, thermal comfort and ventilation were left to good practice and occasional complaints. The revised Energy Performance of Buildings Directive (EPBD, Directive (EU) 2024/1275) changes that. It links energy performance with indoor environmental quality (IEQ), requires building automation and control systems in larger non-residential buildings to monitor IEQ from May 29, 2026, and asks Member States to set standards for healthy indoor climates.
At the same time, hybrid work has made occupancy unpredictable, energy prices remain a board-level concern, and post-pandemic standards such as ASHRAE Standard 241 have put ventilation and filtration under scrutiny. For building owners, operators and facility managers, the result is a clear direction: measure what happens inside buildings, continuously, and use that data to run them better. This article explains the requirements, the sensors that matter, how to design a deployment and how to turn data into savings and healthier spaces.
What the Revised EPBD Requires
The EPBD entered into force in May 2024, with a general transposition deadline of May 29, 2026. Its provisions on IEQ and building automation sit mainly in Article 13. In summary:
- IEQ standards: Member States must set requirements for adequate indoor environmental quality standards in buildings to maintain a healthy indoor climate.
- Building automation and control systems (BACS): where technically and economically feasible, non-residential buildings must be equipped with BACS, by the end of 2024 for buildings with heating, air-conditioning or combined systems above 290 kW, and by the end of 2029 for those above 70 kW.
- IEQ monitoring in BACS: from May 29, 2026, these systems must be capable of monitoring indoor environmental quality, alongside monitoring, analyzing and benchmarking energy use.
- New zero-emission buildings: non-residential zero-emission buildings must be equipped with measuring and control devices for monitoring and regulating indoor air quality.
- Existing buildings: non-residential buildings must install such devices when undergoing major renovation, where technically and economically feasible. Member States may extend requirements to residential buildings.
The directive defines IEQ broadly, covering factors such as temperature, humidity, ventilation rate and the presence of contaminants. National transposition will set the details, so owners operating in several countries should expect variations in thresholds, reporting and enforcement.
Why this matters beyond compliance
Monitoring IEQ is not only a legal checkbox. It exposes the trade-off at the heart of building operation: ventilation and conditioning consume energy, but under-ventilation harms comfort, productivity and health. Without data, operators default to fixed schedules that over-ventilate empty spaces and under-ventilate crowded ones. With data, they can do both better.
Who is affected and how quickly
In practice, the obligations land first on owners of large offices, retail centers, hotels, hospitals, universities and logistics buildings, many of which already crossed the 290 kW threshold and should have had BACS since the end of 2024. The May 2026 IEQ monitoring capability applies to those systems now. The 70 kW threshold brings a much larger group of mid-sized buildings into scope by the end of 2029, which is short given procurement and installation cycles. Portfolio owners should therefore treat 2027 and 2028 as the main delivery window, and plan IEQ sensing into every BACS upgrade and major renovation from today, rather than adding it later at higher cost.
The Sensing Toolkit: What to Measure
The EPBD does not prescribe a sensor list. European frameworks such as EN 16798-1, referenced by industry bodies, recommend monitoring a set of parameters that together describe IEQ. A practical toolkit includes:
Air quality
- Carbon dioxide (CO2): the workhorse proxy for ventilation adequacy relative to occupancy. Use true NDIR sensors rather than estimated “eCO2” from VOC sensors.
- Particulate matter (PM2.5, PM10): important near busy roads, in industrial settings and during wildfire smoke episodes.
- Volatile organic compounds (VOCs): useful as a relative indicator of emissions from materials, cleaning products and activities.
- Specific gases where relevant: formaldehyde, nitrogen dioxide, ozone or radon depending on building type and location.
Thermal comfort
- Air temperature and relative humidity in each zone, not just at the return duct.
- Radiant effects in glazed spaces, which can make readings misleading without context.
Occupancy and use
- Presence detection (passive infrared, radar) for lighting and HVAC control at room level.
- People counting (thermal sensors, time-of-flight, privacy-preserving vision) for space utilization and demand-controlled ventilation.
- Booking and access data from workplace systems, which provide intended occupancy to complement measured occupancy.
Light and acoustics
Illuminance and noise levels complete the IEQ picture and matter for workplace wellbeing standards, although they are less directly tied to energy.
The revised EPBD turns indoor environmental quality from a comfort issue into a measurable building performance metric. Owners who instrument their spaces well will cut energy waste and protect occupants with the same data.
Designing a Monitoring Architecture
A good IEQ program is more than a box of sensors. It is an architecture that connects measurement, control and insight.
Layer 1: Sensors and placement
Place sensors in the breathing zone, away from windows, diffusers, doors and direct sunlight. Prioritize spaces with variable or high occupancy: meeting rooms, classrooms, open-plan areas and auditoriums. Define a sensor density per zone type and stick to it, so data is comparable across buildings.
Layer 2: Connectivity
Wireless sensors simplify retrofits. LoRaWAN suits battery-powered sensors across large buildings and campuses; Wi-Fi and Thread-based options suit powered devices; wired BACnet or Modbus remains standard for sensors that directly control HVAC equipment. Many portfolios use a mix, with gateways translating into the building management system.
Layer 3: Integration with BACS
Monitoring alone does not improve air. Feed IEQ and occupancy data into the BACS so ventilation, heating and cooling respond to actual conditions, for example demand-controlled ventilation driven by CO2 or people counts. Use open protocols and well-documented point naming, ideally with semantic models such as Brick or Project Haystack, so data is portable across systems and vendors.
Layer 4: Analytics and reporting
A cloud or on-premises analytics platform aggregates data across buildings, benchmarks spaces, detects faults (stuck dampers, drifting sensors, simultaneous heating and cooling) and produces reports for compliance, ESG disclosures and occupants. This is where IEQ data meets energy data and space utilization data.
Turning IEQ Data Into Value
Once sensors are installed and integrated, the question becomes what to do with the data. The most valuable use cases fall into four groups.
Energy optimization
- Demand-controlled ventilation: modulate outdoor air based on CO2 or people counts instead of design occupancy, which is often far above actual use in hybrid workplaces.
- Occupancy-based scheduling: set back heating, cooling and lighting in zones that are empty, and pre-condition only the spaces that bookings and historical patterns show will be used.
- Space consolidation: use utilization data to close floors or wings on low-occupancy days and concentrate people where systems run efficiently.
Fault detection and diagnostics
Persistent anomalies in IEQ data often point to mechanical faults: high CO2 with ventilation nominally running suggests a stuck damper or a mis-set schedule; temperatures that swing between heating and cooling setpoints suggest control conflicts. Automated rules that compare sensor readings with BACS states catch these issues weeks before complaints arrive.
Occupant experience and wellbeing
Sharing simple indicators, such as a traffic-light display in meeting rooms or an app showing which spaces have the best conditions, builds trust and lets people choose where to work. It also creates accountability: if a space repeatedly goes red, facility teams are expected to act.
Reporting and valuation
IEQ and energy data together support sustainability disclosures, green building certifications and tenant reporting. For owners and investors, documented indoor quality increasingly forms part of how a building’s quality and future value are judged.
A Buyer’s Checklist for IEQ Sensors and Platforms
- Stated accuracy and long-term stability for each parameter, with automatic baseline correction explained for CO2 sensors.
- Calibration and replacement intervals, and whether calibration can be checked in the field.
- Battery life at the intended reporting interval, and the impact of more frequent reporting during control use.
- Supported protocols (LoRaWAN, BACnet, Modbus, MQTT) and the availability of open APIs for data export.
- Security features, including unique device credentials, encrypted communication and signed firmware updates.
- Privacy design for any occupancy technology, with clear documentation of what is and is not captured.
- Vendor roadmap and support commitments matching the expected life of the installation.
Using ASHRAE 241 and Infection-Risk Planning
Outside the EU framework, ASHRAE Standard 241, approved in 2023, introduced the concept of an equivalent clean airflow rate: the combined effect of outdoor air, filtration and air disinfection delivered to occupied spaces. It defines an infection risk management mode for periods of elevated risk and requires a building readiness plan. Even where it is not mandatory, it offers a useful framework for multinational owners: IEQ monitoring provides the evidence that systems perform as planned, and occupancy data helps decide when to switch modes.
A Step-by-Step Implementation Plan
- Map obligations per building. Identify which buildings exceed the 290 kW and 70 kW thresholds, which are planned for major renovation, and which national rules apply after transposition.
- Assess existing BACS capability. Can it ingest IEQ data, control ventilation on demand and export data? Many older systems need upgrades or an overlay platform.
- Define the sensing standard. Parameters, accuracy requirements, placement rules and sensor density per space type.
- Pilot in two contrasting buildings. For example, a modern office and an older building with constant-volume ventilation, to understand the range of challenges.
- Integrate control. Implement demand-controlled ventilation and occupancy-based schedules, with safety margins and override procedures.
- Establish analytics and reporting. Dashboards for facility teams, KPIs for management and occupant-facing displays where appropriate.
- Scale across the portfolio. Roll out in waves, prioritizing buildings with the greatest compliance exposure or energy savings potential.
- Maintain and calibrate. Schedule sensor calibration checks, battery replacements and firmware updates; monitor data quality automatically.
A Worked Example: A Mid-Sized Office Portfolio
Consider a generic property company with a dozen office buildings in two EU countries, several of which have heating and cooling systems above 290 kW. Hybrid work has left average occupancy far below design levels, but meeting rooms are crowded on peak days.
The company starts with an audit: three buildings have BACS that can accept additional data points, two have outdated systems, and the rest fall between the thresholds and will need BACS by 2029. It defines a sensing standard (CO2, temperature, humidity, PM2.5 and people counting in meeting rooms; CO2, temperature and humidity in open areas) and installs wireless sensors over LoRaWAN, connected to the BACS through gateways and to a central analytics platform.
In the pilot buildings, demand-controlled ventilation reduces air handling during low-occupancy days while keeping CO2 within agreed targets during peaks. Analytics reveal a floor where a damper fault caused persistent high CO2, fixed within days. Occupancy data shows that a whole wing is rarely used on Mondays and Fridays, allowing the company to consolidate those days into fewer zones. IEQ reports become part of tenant communications and ESG reporting, and the company has evidence ready for national compliance checks.
Pitfalls to Avoid
- Cheap sensors with poor accuracy. Inaccurate CO2 or PM readings erode trust and lead to bad control decisions. Specify accuracy and verify it.
- Monitoring without control. Dashboards that do not change HVAC behavior miss most of the energy and comfort benefit.
- Privacy concerns with occupancy sensing. Prefer anonymous counting technologies, communicate clearly with occupants and works councils, and avoid tracking individuals.
- Proprietary lock-in. Insist on open protocols, data export and documented point lists.
- Neglecting maintenance. Sensors drift and batteries die; budget for lifecycle management from the start.
Outlook
IEQ monitoring is likely to become a standard part of building performance certificates, green leases and investor due diligence. Expect closer integration between IEQ data, digital twins of buildings and AI-driven HVAC optimization, and growing interest from insurers and lenders in evidence of healthy, efficient buildings. As national transpositions of the EPBD settle, owners with a scalable sensing architecture will be able to adapt to local thresholds without starting over.
Conclusion
The revised EPBD makes indoor environmental quality a core part of how European buildings are designed and operated. Building automation systems must now be able to monitor IEQ, new zero-emission buildings need air quality monitoring and control, and renovations bring existing buildings into scope. The opportunity is to use one sensing and data architecture to meet obligations, cut energy waste and create healthier spaces. Start with an obligation map and a clear sensing standard, integrate with control, and treat data quality as an ongoing discipline.
How Hanoi Technology Can Help
Hanoi Technology designs and integrates indoor environmental quality and occupancy sensing, connecting sensors, building automation and analytics into one managed data platform.
Further Reading
- Directive (EU) 2024/1275, Article 13 – Technical building systems and IEQ (text via LawPlayer)
- IEQ finally enters the EPBD: linking energy performance and indoor environment – Swegon Air Academy
- ASHRAE approves groundbreaking standard to reduce the risk of disease transmission in indoor spaces – ASHRAE