Background
The impact of climate change is increasingly felt in cities, where extreme weather events such as prolonged heat waves are exacerbated by the urban heat island effect. With more than 55% of the world's population residing in cities, it has become crucial to address the climatic challenges in urban areas. This urgency has led to the development of the new Annex "Sustainable Cooling in Cities," which focuses on implementing climate actions in urban agglomerations.
First, there is an immediate need for effective measures to improve outdoor climate conditions in cities, ensuring comfortable and healthy living environments. This requires interventions at different spatial scales, from city-wide urban design to neighborhood-level initiatives and building-specific strategies. Urban design and landscaping can play a key role in optimizing urban morphology to enhance air and wind movement while integrating green and blue infrastructures to offer shade and lower outdoor temperatures. Additionally, utilizing cool materials in outdoor spaces can directly benefit people and indirectly improve indoor living conditions.
Second, cities need strategic solutions to address the cooling requirements of buildings: first, to reduce the cooling need, and second, to meet it in an energy-efficient, climate-friendly, socially beneficial and affordable way. The increasing demand for building cooling necessitates innovative approaches that consider the urban context. Instead of relying solely on decentralized air conditioning units, which contribute to heat and noise pollution as well as inefficient energy usage, cities should explore cooling methods such as district cooling, seawater cooling, and radiative cooling. Implementing balanced cooling and heating with seasonally balanced environmental heat sinks can further optimize energy use and reduce the environmental impact.
Third, the interdependence between outdoor climate mitigation and sustainable building cooling must be acknowledged. Sustainable cooling technologies depend ona favorable utdoor climate, making it essential to mitigate urban heat waves. Failure to address outdoor climate challenges can compromise the effectiveness of cooling strategies during extreme weather conditions. Conversely, the excess heat from air conditioners can significantly impact outdoor comfort especially during heat waves.
Objectives
The project aims to expand and share international knowledge on effective heat mitigation and sustainable cooling in cities. Emphasis will be placed on the interaction between heat mitigation in outdoor spaces and building cooling. The goal is to develop and support the application of measures that serve the health, safety and wellbeing of people while promoting energy efficiency and paving the way toward carbon neutrality.
The project has four sub-objectives.
Fundamentals. The first sub-objective is to establish a knowledge base on environmental quality criteria in indoor and outdoor spaces, as well as key performance indicators (KPIs) for urban cooling. The KPIs will assess the sustainability and resilience of cooling solutions. This will consider indoor and outdoor air quality and comfort, health, productivity, safety, energy efficiency, environmental impact, and cultural, social, and economic aspects. It will also involve extracting and processing knowledge about human-centric indicators such as heat vulnerability indexes.
Methods. The second sub-objective is to develop both simulation and experimental methods to assess heat mitigation and cooling technologies. This includes evaluating simulation tools as well as identifying and developing experimental evaluation methods for urban heat and its countermeasures.
Solutions. The third sub-objective is to identify and assess solutions to improve heat mitigation in urban outdoor areas and cooling in buildings, focusing on the interrelation of both measures. This will involve investigating measures such as urban design, airflow, shading, evaporation, cool materials, district cooling, and usage of natural heat sinks. The focus will be on “low-tech”, robust, and affordable technologies, considering technical-energetic and socio-economic aspects.
Policy. The fourth sub-objective is to apply scientific research and results to real-world applications, identify best practices for policy-making, and strengthen existing networks to enhance global adoption of sustainable cooling practices.
The project aligns with the current EBC Strategic Plan 2019 – 2024, focusing on:
- Reinforcing the technical and economic basis for refurbishing existing buildings
- Improving planning and construction processes
- Creating low-tech, robust, and affordable technologies
- Further developing energy-efficient cooling
- Developing holistic solution sets for district-level systems
Scope and Limitations
The Annex focuses on implementing cooling measures in urban areas, including heat mitigation, outdoor space cooling, and sustainable cooling of buildings. The Annex will address three scales:
- Large—the whole city
- Medium—neighborhoods
- Small—immediate building surroundings
The Annex will explore building cooling solutions suitable for urban environments, seeking to avoid negative side effects and leveraging synergies with other urban energy processes, such as heating or domestic hot water.
The project will emphasize the interrelation between outdoor heat mitigation and sustainable building cooling. It will build upon existing knowledge of human well-being and comfort, as well as key performance indicators for sustainable cooling in cities.
The assessment and development of solutions will concentrate on their application in existing buildings and spaces, emphasizing low-tech, robust, and affordable technologies. The project aims to identify and reduce performance deficits and gaps, considering technical-energetic and socio-economic aspects.
However, cost assessments across different countries are not feasible and will not be conducted.
The project will explore various technologies and approaches, including urban design, airflow, shading, evaporation, cool materials, district cooling, natural heat sinks, cool surfaces, sky radiative cooling, solar cooling, and behavioral adjustments. The investigation will focus on nature-based solutions (e.g., blue and green infrastructures, airflow), mechanical solutions (e.g., advanced air conditioning, radiative cooling, and district cooling), gray solutions (i.e., design strategies and interventions in the built environment for better shading and ventilation), and soft solutions (i.e., operational and behavioral measures).
Case studies will be integrated into reports but will not constitute a separate subtask.
The project specifically targets cooling in cities and urban agglomerations and excludes rural environments because more than 55% of the global population resides in cities and urban areas, which have unique needs and challenges for sustainable cooling. The aim is to address all climate zones relevant to heat mitigation and cooling without excluding any specific climate.
Means
Based on these findings, the new Annex proposes research and development at the intersection of urban design and building technology.
Interest in this new Annex has been expressed not only by the ExCo of the TCP Energy in Buildings & Communities, but also the ExCo of the TCP Cities, which has evolved from the EBC Annex 63 and later EBC working group on Cities and Communities. It is planned , and required for national funding of the Operating Agent, to undertake the new Annex as a joint research project between the two Technology Collaboration Programs Energy in Buildings and Communities (EBC) and Cities TCP.
The Annex is structured in four Subtasks.
A. Fundamentals
B. Methods
C. Solutions
D. Policy