Background

The new Annex, “Air Cleaning for Sustainable and Resilient Buildings” builds on the foundation of IEA EBC Annex 78, extending the focus from gas-phase air cleaning to a comprehensive integration of technologies addressing both particulate and gaseous pollutants. It responds directly to the challenges of achieving the goals of the Energy Performance of Buildings Directive (EPBD) across the European Union, where maintaining indoor air quality (IAQ) in increasingly airtight, energy-efficient buildings has become a key concern. Traditional solutions that rely on increasing ventilation rates often improve IAQ but come at the cost of higher energy consumption and the potential introduction of outdoor pollutants, such as PM2,5, allergens, airborne pathogens, or wildfire smoke. This Annex recognizes that the next generation of sustainable buildings must achieve a balance between health, comfort, and energy performance by integrating air cleaning systems as an essential complement to ventilation.

The Annex will explore how advanced air cleaning technologies, including mechanical filtration, activated carbon, photocatalysis, plasma, ionization, and UV disinfection, can be combined with ventilation systems to create energy-efficient air change rates strategies that maintain IAQ while reducing heating and cooling loads. The work will develop standardized performance metrics, such as the Clean Air Delivery Rate per kilowatt-hour (CADR/kWh), to evaluate and compare the efficiency of different systems. The Clean Air Delivery Rate per kilowatt-hour (CADR/kWh) metric will be defined to represent the effective clean air delivery for both particulate and gaseous pollutants, including VOCs and ozone. Consideration will also be given to tiered performance ratings  analogous to existing filtration classifications (e.g., MERV or ePM levels) to ensure comparability and scalability across technologies. It will also establish guidelines for technology selection, design, and operation, enabling consistent application across climates and building types. By enabling optimized air recirculation and reducing reliance on traditional ventilation, these solutions directly contribute to the implementation of the EPBD and its objectives for energy efficiency, sustainability, and occupant health.

The Annex is motivated by the increasing need for resilient building operation under conditions of climate stress and environmental emergencies. Events such as wildfires, overheating, and infection outbreaks have demonstrated that ventilation alone is insufficient to ensure healthy indoor environments. Integrating air cleaning technologies can help maintain safe IAQ when outdoor air is polluted or when ventilation energy use must be limited. The Annex will therefore address resilience as a central theme, establishing a scientific and practical framework for using air cleaning as a tool to maintain comfort and safety during extreme events while supporting long-term energy and climate goals.

Research activities will focus on several key questions: What is the optimal balance between air cleaning and ventilation to minimize energy use while maintaining IAQ? How can performance be consistently assessed through standardized metrics such as CADR/kWh? How do environmental factors such as temperature, humidity, and pollutant load influence system performance in real world applications? How can long-term field data be used to validate models and improve testing protocols? And how can these findings inform the EPBD’s ongoing implementation and future revisions? Addressing these questions will provide the technical basis for improved building design, operation, and policy guidance.

The Annex will deliver practical and policy-relevant outcomes for multiple stakeholders. Policy makers and regulators will receive a framework linking air cleaning performance to EPBD compliance. Designers, engineers, and consultants will gain tools for integrating air cleaning into ventilation systems without compromising energy targets. Manufacturers and testing bodies will benefit from harmonized standards and performance metrics that facilitate certification and market adoption. Researchers will have access to validated data and models that support future development and standardization efforts. The results will be disseminated through reports, workshops, peer-reviewed publications, and a public knowledge platform, ensuring effective knowledge transfer between research, industry, and policy communities. 

By combining scientific evidence with practical implementation guidance, this Annex will help Europe move toward a sustainable, resilient, and health-centered building stock. It will close critical knowledge gaps, reduce the energy burden of ventilation, improve occupant well-being, and enhance the resilience of buildings in the face of climate and health-related challenges. In doing so, it will directly support the Energy Performance of Buildings Directive (EPBD) and the broader European vision of a climate-neutral, adaptive, and people-centered built environment.

Justification

The new Annex has evolved from expert discussions held during and after IEA EBC Annex 78, which investigated the energy performance of gas-phase air cleaning technologies. Those discussions, together with recent research in Annex 87 (Energy and Indoor Environmental Quality Performance of Personalised Environmental Control Systems), Annex 86 (Energy Efficient Indoor Air Quality in Buildings) and Annex 88 (Health and Indoor Climate), revealed the growing need for a broader and integrated approach that includes both particulate and gaseous pollutant control, linked directly to energy performance, resilience, and regulatory implementation.

This Annex responds to the increasing importance of indoor air quality (IAQ) in the context of Europe’s Energy Performance of Buildings Directive (EPBD), which calls for buildings that are not only energy-efficient but also healthy, resilient, and adaptive to climate change. As buildings become more airtight and energy-efficient, the traditional approach of improving IAQ through higher ventilation rates becomes less viable, leading to higher energy use and the potential introduction of outdoor pollutants such as fine particles or wildfire smoke. Therefore, integrating air cleaning technologies as part of building ventilation strategies has become essential for balancing energy efficiency, health, and comfort.

The Annex is justified by three main drivers. First, energy efficiency and decarbonization—air cleaning can reduce ventilation energy demand by enabling optimized air recirculation while maintaining indoor air quality (IAQ), thereby supporting the EPBD’s objective of lowering building-related energy use and carbon emissions. Second, health and indoor environmental quality—by controlling both particulate matter and gaseous pollutants, air cleaning contributes to the creation of healthy indoor environments in line with WHO IAQ guidelines and the EU’s “zero pollution” ambition. Third, resilience and climate adaptation—air cleaning enhances building resilience during external air pollution episodes, wildfires, overheating periods, or infection outbreaks, ensuring safe and adaptive operation under changing climatic conditions.

The Annex will address several critical research and policy needs. It will focus on developing standardized performance metrics, such as the Clean Air Delivery Rate per kilowatt-hour (CADR/kWh), to evaluate both energy and indoor air quality (IAQ) performance and health risk due to airborne pathogen. It will also assess combined ventilation and air cleaning strategies through modeling and field demonstrations in non-residential buildings. Furthermore, the Annex will investigate long-term performance and operational impacts under real environmental conditions—including variations in temperature, humidity, and pollutant composition. In addition, it will provide guidance for regulation, certification, and design to promote harmonized  implementation across the EU. Finally, the Annex will generate real-world data and validation to support the ongoing revision of the EPBD and facilitate effective national implementation strategies. 

By linking indoor air quality, energy efficiency, and building resilience, this Annex directly supports the European Union’s transition toward a sustainable, decarbonized, and health-centered building stock. It fills the current gap between research, technology, and policy by providing a unified framework for
integrating air cleaning into energy-efficient building design and operation.

Objectives and Scope

Annex Vision
The vision of the proposed Annex is to provide building owners, designers, operators, policymakers, and industry stakeholders with a structured framework of concepts, procedures, tools, and evidence that supports the efficient, resilient, and health-centered integration of air cleaning technologies in buildings.

The Annex aims to position air cleaning as a core element of sustainable ventilation strategies, ensuring that energy efficiency, indoor air quality (IAQ), and resilience are achieved simultaneously in line with the Energy Performance of Buildings Directive (EPBD). By developing harmonized performance metrics and implementation guidelines, the Annex will enable buildings that are both low-carbon and health-promoting, even under challenging environmental  conditions.

Annex Scope
The focus of the proposed Annex is on developing and validating energy-efficient, IAQ-improving, and climate-resilient air cleaning solutions for non-residential buildings. The Annex will examine technologies addressing both particulate pollutants (PM2,5, allergens, airborne pathogens) and gaseous contaminants (VOCs, odors, ozone, CO2), and their integration with ventilation systems to support EPBD implementation across Europe.

The scope related to concepts, procedures, and tools for integrating air cleaning encompasses several key activities. It includes the development of standardized performance metrics, such as the Clean Air Delivery Rate per kilowatt-hour (CADR/kWh) -The CADR/kWh metric will address both particulate and gaseous pollutants, with possible tiered performance ratings comparable to MERV/ePM leve; the definition of design and control principles for combining ventilation and air cleaning to reduce energy demand; the creation of models and assessment tools to optimize system design and monitor performance; and the establishment of guidelines and regulatory recommendations to ensure harmonized adoption across EU member states. In addition,  the Annex scope covers field studies and living lab demonstrations to validate long-term energy and indoor air quality (IAQ) performance; scenario analyses to assess system resilience under conditions such as wildfire smoke, overheating, and infection events; evaluation of cost-effectiveness and life-cycle energy use to support sustainable implementation; and identification of standardization needs to ensure consistent testing and certification of air cleaning technologies.

Annex Objectives
The objectives of the Annex are to:

• Develop a comprehensive framework for integrating air cleaning technologies into energy-efficient ventilation concepts aligned with the EPBD.
• Define performance-based metrics and methods (e.g., CADR/kWh) to evaluate energy and IAQ outcomes.
• Establish guidelines and modeling tools that support design, control, and operation of combined systems.
• Validate long-term field performance and user experience through case studies and demonstration projects.
• Provide scientific and regulatory evidence to inform future EPBD revisions and European standardization.
• Enhance industry awareness and competence through data-driven research, workshops, and dissemination activities.