Extreme heat is becoming one of the most urgent climate, health and development risks facing cities, but its impacts are often most dangerous inside the homes least equipped to withstand it. The latest Cool Talks session, Extreme Heat Action in Cities and Communities, brought together researchers, city practitioners and implementation partners to examine how passive cooling, community led housing upgrades and local heat action can help protect vulnerable communities without increasing energy demand or emissions.

Moderator Ekta Jhaveri, Program Manager, Climate Health at the William Davidson Institute, opened the event by framing extreme heat as a climate, health and development risk that is becoming increasingly acute in cities, especially in dense, low income and informal settlements. “Reducing heat risk without increasing energy demand or emissions is a formidable challenge,” she said, pointing to passive cooling, heat action and subnational implementation as practical entry points.

Passive cooling for informal homes and self-built settlements

The first panel examined indoor heat exposure in informal and self-built housing, moving from the risks inside homes to the design and community delivery of passive cooling interventions. Ana Paula Pimentel Walker, Associate Professor in Urban and Regional Planning at the Taubman College of Architecture and Urban Planning, University of Michigan, argued that current heat adaptation efforts still overlook the home, one of the most important risk environments. “Indoor heat remains largely unmeasured, unregulated and overlooked, despite being where people spend most of their time during heat waves,” said Pimentel Walker. Based on research in Brazil and Colombia, she showed how poor infrastructure, limited green space and low-cost construction materials can create dangerous indoor conditions, and outlined a community led approach that combines thermal modelling, passive cooling retrofits and local knowledge to improve thermal comfort without increasing energy demand. 

Gabriel Harp, Director of Research and Creative Practice Development at the Taubman College of Architecture and Urban Planning, University of Michigan, focused on how passive cooling solutions can be assessed and communicated before implementation. Harp explained how the team uses information on building structures, materials, dimensions and household practices to create computer models that compare passive cooling options before interventions are made. As a worked example, he showed mud-brick homes in Burkina Faso modelled with different roof types, comparing steel and mud-brick roofs to identify which modifications would have the greatest impact before any costly changes are made to people's homes. These findings are then translated into visual materials that help communities and implementation teams understand the trade-offs between different measures, from cross ventilation and second ceilings to solar chimney systems.

Julian Constantino Carvajal, Independent Legal Consultant and former Land Legalization Coordinator for the Municipality of Bucaramanga, brought the municipal and community implementation perspective from Luz de Salvación II in Colombia. The settlement, established in 2001, now holds around 430 houses and close to 1,000 residents, part of a cluster of seven informal settlements housing some 2,200 people. Carvajal explained that the work in Bucaramanga focused on recognizing informal settlements and supporting access to basic services such as water, sewage and gas. In Luz de Salvación II, he presented an ongoing retrofit of a community centre that combines a secondary roof, fiberglass insulation and thermal coating on the existing metal sheet roof, demonstrating how locally identified priorities can be translated into practical passive cooling interventions. 

Together, these presentations illustrated the interdisciplinary work of the Heat, Health, and the Built Environment cluster at Taubman College and its university‑wide and global collaborators in developing context‑sensitive, community‑driven solutions to reduce indoor heat exposure.

Scaling heat action across cities and institutions

The second panel shifted from household and settlement level cooling to the systems needed to scale local heat action across cities, communities and institutions. Opening the discussion, Eva Gurria, Partnerships and External Relations Lead for the NBSAP Accelerator Partnership, framed urban heat as a biodiversity and resilience challenge as well as a climate issue. Gurria said nature-based solutions should be treated as cooling infrastructure, not decorative greening, because trees, wetlands, blue green spaces and green corridors can reduce heat while also supporting air quality, flood management, water security and biodiversity. “When we lose biodiversity and ecosystem functions in cities, we also lose nature’s natural cooling capacity,” she said. With policy frameworks increasingly in place, Gurria stressed that the priority now is implementation through urban cooling in biodiversity planning, investment in green and blue infrastructure, and stronger links between cities, finance, technical support and partnerships.

Aynur Kadihasanoglu, Senior Urban Specialist at the Red Cross Red Crescent Climate Centre, focused on the last mile of heat resilience. Drawing on Heat Action Day, held annually on 2 June, she showed how global awareness can translate into locally designed action on indoor heat, from homes and schools to workplaces and care settings. She stressed that effective heat action depends on linking communities with city authorities and national systems, so that preparedness is not reduced to messaging after the fact. “A lot of actions are designed without really understanding the perceptions,” she said, noting that misconceptions about heat health risks remain common among affected communities, caregivers and health professionals. For Kadihasanoglu, understanding how people perceive risk is essential to making early warning, anticipatory action and simple protective measures work before extreme heat becomes life threatening.

Building on Kadihasanoglu's focus on community preparedness, Elsa Lefèvre, Programme Manager for Beat the Heat in UNEP's Subnational Climate Action Unit, addressed how cities can move from awareness to delivery. She presented Beat the Heat as the delivery mechanism for the Global Cooling Pledge, helping translate political commitments into city level action through heat mapping and planning, nature-based solutions, passive cooling, public procurement and sustainable cooling incentives. More than 240 cities and over 100 partners have joined the initiative, but early survey findings point to a clear implementation gap. "Cities are already ranking extreme heat as a top three risk, but at the same time almost half of them have not yet started to do the basic mapping or planning," she said. Yet planning proves to be the decisive lever: cities that have completed heat mapping or planning are more than eight times more likely to have begun implementing nature-based solutions for cooling.

Greening as infrastructure

With the panels concluded, the Q&A turned to how cities can make the case for investment and move from isolated interventions to wider delivery. Speakers highlighted that urban greening should be assessed as infrastructure, since trees, parks, wetlands and blue green systems can deliver cooling, stormwater management, air quality and public health benefits that would otherwise require costly engineered solutions. The exchange also pointed to natural capital accounting, ecosystem service valuation and tools such as BIOFIN as ways to quantify the long-term value of nature-based cooling. Financing was framed as a blended effort rather than a single funding stream, combining municipal seed funding, private sector engagement, stewardship models and technical support. 

The session underscored that protecting communities from extreme heat will require action at every level, from homes and neighbourhoods to city systems and national frameworks. Passive cooling, nature-based solutions, community preparedness and heat planning are no longer separate agendas. Together, they offer a practical pathway for cities to reduce heat risk, protect vulnerable people and scale sustainable cooling without locking in higher energy demand or emissions.