Background

Decarbonization of residential buildings is intended to both improve energy efficiency and reduce or eliminate the use of fossil fuels. Decarbonization also has the potential to generate significant co-benefits for occupant comfort and health. These additional effects, known as co-benefits or non-energy impacts (NEIs), refer to outcomes that are not directly related to energy use. NEIs, particularly those related to health, have been studied for more than three decades. However, despite a strong understanding of the health impacts associated with specific indoor contaminant exposures, substantial gaps remain in identifying strategies that enhance these co-benefits, as well as in quantifying the broader health and societal benefits of decarbonization and translating them into measurable outcomes.

A previous WHO study identified housing as a critical public health issue, quantifying the annual environmental disease burden (including mortality) per 100,000 people using Disability-Adjusted Life Years (DALYs) to provide a standardized measure of prevalence. The results showed how poor housing conditions, such as low indoor temperatures, second-hand smoke, radon, and solid fuel use contribute to deaths, while mold, traffic noise, and unsafe home features result in significant DALYs lost. Inhalation of contaminants from combustion byproducts has been shown to contribute to various adverse health effects at the population level. A previous study identified key combustion-related pollutants that pose significant indoor health risks in homes, including acetaldehyde, acrolein, benzene, formaldehyde, NO2, and PM2.5. The study emphasized the critical role of adequate ventilation in mitigating exposure to these pollutants and consequently reducing associated health risks. A recent study quantified the chronic health impacts of indoor air contaminants in residential homes using DALYs. The study identified PM2.5, PM10-2.5, NO2, and formaldehyde as the most harmful pollutants prevalent in dwellings, originating from several sources. Together, these pollutants accounted for over 99% of the total harm. These findings underscore the importance of aligning decarbonization measures (such as electrification and envelope tightening) with IEQ management to avoid unintended increases in exposure.

Several previous IEA Annexes and tasks have carried out investigations and have obtained results that will be relevant to this Annex, such as EBC Annexes 5,86, 87, and 92. This proposal builds on and integrates these efforts by introducing a project that explicitly links decarbonization pathways with IEQ and health outcomes

In some ways this proposal is an extension of ANNEX 86 “Energy Efficient Indoor Air Quality Management in Residential Buildings” by expanding beyond energy efficiency to focus on assessing and quantifying the IEQ improvements and impacts that were not included in ANNEX 86.  Much of what was learned in ANNEX 86 will be background material for this new Annex, and many of the same researchers and subject matter experts will be involved.

IEA EBC ANNEX 5 “Air Infiltration and Ventilation Centre“ also has a strong connection to this proposal, with ANNEX 5 conference topics and research agenda now being directed towards decarbonization. Many of the people interested in the proposed new Annex are active participants in ANNEX 5. ANNEX 5 will be a strong venue for disseminating the results of this proposed Annex.

While having a very different focus and core technical basis, this proposed annex would be highly complementary to both ANNEX 92 and ANNEX 87 - both of which are doing related IEQ work, while noting that this new Annex will consider only residential buildings.

Objectives and Scope

Aim

This Annex aims to advance evidence-based strategies for residential building retrofits for decarbonization that simultaneously improve IEQ, occupant health and comfort, and energy performance. By integrating renewable energy systems, energy conservation measures, and performance monitoring, the project seeks to develop practical, affordable, and resilient retrofit solutions that minimize peak power demand, enhance grid stability, and reduce exposure to indoor environmental hazards. Through interdisciplinary research and stakeholder engagement, it will evaluate the effectiveness of these strategies and provide robust tools and guidelines to support the implementation of energy-efficient, health-promoting, and climate-resilient retrofit solutions.  Critically, the inclusion of a stakeholder panel will ensure that practical considerations for manufacturers, contractors, workforce development programs, disadvantaged communities, and policymakers will be embedded in the outcomes and enhance broad impact.

Key research foci that this Annex will include are:

Monitoring and Evaluation

• Establish systems for both short- and long-term monitoring of retrofitted buildings to assess performance and effectiveness.
• Use measured data to refine retrofit guidelines, design practices, and policy frameworks.
• Develop modelling tools to predict and evaluate building performance.
• Implement occupant feedback mechanisms to ensure continuous improvement and adaptation of retrofit strategies.

Energy Considerations

• Maintain energy efficiency, decarbonization, and resilience as core priorities in retrofit strategies.
• Enhance energy flexibility to allow residential buildings to integrate renewable energy and adapt to variable supply conditions.
• Strengthen energy resilience through energy storage solutions and robust energy management systems.

Interdisciplinary Collaboration

• Partner with public health experts to evaluate and communicate the health benefits of improved IEQ.
• Collaborate with social scientists and economists to assess the socio-economic impacts of retrofits and promote socially acceptable, cost-effective solutions.

Translating Research into Practice

• Develop practical tools and user-friendly guidelines for stakeholders (e.g., manufacturers, contractors, architects, engineers, policymakers) to harmonize IEQ and decarbonization strategies effectively.
• Conduct pilot projects and case studies to demonstrate and validate real-world applications, documenting lessons learned and best practices.

Stakeholder Engagement

• Establish, as a part of the project, an official Stakeholder Panel that includes representatives from industry, contractors, policy, and disadvantaged communities.
• Include observers from countries not typically engaged in Annexes.
• Foster industry collaboration with construction firms, HVAC manufacturers, and building management companies to ensure solutions are feasible and scalable.
• Engage policymakers to translate research outcomes into effective policies, incentives, and regulations that promote energy-efficient retrofits with improved IEQ.

EBC Strategic Plan 2024-2029

This proposed Annex directly aligns with the EBC Strategic Plan 2024–2029 by addressing the priority of advancing evidence-based strategies for energy-efficient, resilient, and health-promoting residential building retrofits. By integrating energy performance, grid flexibility, and IEQ improvements, the project responds to the Plan’s emphasis on demand-led approaches, energy efficiency, and managing peak loads to support broader energy system stability. The Annex also embodies the strategic goal of achieving societal impact through health, comfort, and wellbeing benefits, while translating research into practical tools, guidelines, and case studies for policymakers, designers, and industry stakeholders, thereby closing the performance gap between retrofit design and real-world outcomes.

The project further supports the Plan’s focus on interdisciplinary collaboration and international coordination. By formally engaging with stakeholders from industry, disadvantaged communities, workforce development, policy, and contractors, along with engineers, health experts, social scientists, and economists, and collaborating with related TCPs and organizations (ASHRAE, CIBSE, REHVA, ISO, CEN), the Annex ensures practical, scalable solutions while avoiding duplication of research efforts. Its integration of monitoring, modelling, and stakeholder engagement reflects the Plan’s objectives to enhance research impact, facilitate knowledge exchange, and strengthen governance processes. Overall, the Annex exemplifies the EBC Strategic Plan’s priorities by combining innovation, real-world applicability, and measurable societal, environmental, and energy benefits in residential retrofits.

Target Audience

The target audience for this Annex can be grouped into five key categories:

Researchers and professionals

• Researchers in building science, indoor environmental quality, energy systems, public health, and social sciences will gain knowledge on interdisciplinary methods for evaluating and optimizing the co-benefits of residential energy retrofits. This includes developing metrics, models, and monitoring approaches to assess IEQ, occupant health, and energy performance.

HVAC and building systems manufacturers

• Industry partners will benefit from guidance on designing and implementing retrofit solutions that integrate energy efficiency, renewable energy, and IEQ improvements. Case studies, demonstration projects, and performance data will support the development of scalable, resilient, and cost-effective systems.
• (They need optimized synthesis and test methods for novel materials, design guidelines for new HVAC systems using smart materials, case studies, and demonstration of new system solutions, etc.)

Building designers and consultants

• Architects, engineers, and consultants will gain access to tools, guidelines, and datasets to support the selection and integration of retrofit strategies that optimize energy performance and indoor environmental quality across diverse housing types and climates.

Policy, regulatory and standards bodies

• Policymakers and regulators will receive evidence-based frameworks and metrics to evaluate retrofit solutions in terms of occupant health, IEQ, and energy system flexibility. This will inform policies, incentives, and standards that promote energy-efficient, healthy, and resilient residential buildings without creating barriers to innovation.

Building owners and end-users

• End-users will be the ultimate beneficiaries, experiencing improved comfort, IAQ, and overall wellbeing. They will benefit through other stakeholders such as manufacturers and contractors. We will ensure that end-users, especially from disadvantaged and underrepresented communities, are represented on our stakeholder panel.