Heat Resilient Design: How City Leaders Use Building Materials to Fight Urban Heat
Extreme heat is one of climate change’s most urgent and rapidly growing consequences, especially in cities. Urban areas are particularly vulnerable because they trap heat in building materials and urban streets, creating dangerous conditions for residents. As temperatures continue to rise and heat waves lengthen, cities are grappling with how to remain livable in the face of this intensifying threat.
One response has been creating a new municipal role: the Chief Heat Officer. Appointed in cities from Freetown to Miami, these leaders protect residents from extreme heat by focusing on long-term climate strategies and immediate interventions that reduce heat exposure. Most of these extreme heat leaders are women; many have public health, sustainability, and urban planning backgrounds. They coordinate across government agencies and work closely with communities to put heat at the center of urban planning and design.
Each city approaches the challenge differently, but these efforts are forming a growing guide for addressing extreme urban heat. Chief Heat Officers are introducing new materials, designing cooler buildings and streetscapes, and integrating shade and vegetation into the urban fabric. Collaborating with architects, engineers, and planners reshapes how cities respond to climate impacts. Instead of treating heat as a secondary issue, they address it as a core challenge and create models for protecting the most heat-vulnerable communities.
Cooling Canopies as Public Infrastructure in Freetown, Sierra Leone
Many residents work and shop in informal markets in Freetown, which faces severe and growing risks from extreme heat. Often unpaved and exposed, these markets lack the infrastructure to protect vendors and customers from high temperatures. Eugenia Kargbo, Freetown’s Chief Heat Officer, has responded with a practical, community-focused approach that reflects the daily realities of life in one of the world’s most heat-vulnerable cities.
Working closely with vendors and local stakeholders, Kargbo led the installation of modular shading structures that reflect sunlight and allow air to circulate. Lightweight and adapted to each market’s layout, these canopies are built from materials chosen for durability and cooling performance. At the same time, the city is planting trees to expand the natural canopy, offering shade and reducing heat through evapotranspiration. Vendors have reported being able to work longer hours without discomfort, a meaningful improvement to daily life.
Freetown’s strategy demonstrates that combating urban heat does not always require large-scale infrastructure. Low-cost, high-impact interventions, rooted in local needs, can reduce heat exposure and improve quality of life. For cities with limited resources, this model offers a replicable blueprint for action.
Cool Roofs on Public Buildings in Santiago de Chile
While Freetown addresses heat in informal markets, Santiago targets institutional infrastructure to reduce urban temperatures. Under the leadership of Chief Heat Officer Patricia Pastén Valdés, the city is transforming the rooftops of public buildings into climate adaptation assets.
One of the most ambitious projects is underway at the Hospital de Maipú, where more than 1,000 square meters of green roofing have been installed. These systems include a waterproof membrane, drainage layer, engineered soil, and native or drought-tolerant plants. The layers work together to insulate the building, reduce cooling demands, and manage stormwater. Staff and patients also provide a much-needed connection to greenery.
To support broader implementation, Santiago is gathering performance data from pilot sites to evaluate the benefits of green roofs. The city is developing design standards for durability, maintenance, and thermal efficiency. Santiago’s experience reframes green roofs not as design extras but as essential infrastructure that supports health, comfort, and sustainability.
Reflective Surfaces in Athens, Greece
Athens experiences some of the most extreme urban heat in Europe. During summer, temperatures often rise above safe limits, and the heat is absorbed by streets and public spaces paved in dark, dense materials. Recognizing that the built environment is a significant factor in heat retention, Chief Heat Officer Elissavet Bargianni has launched a citywide program focused on reflective materials.
Athens is applying high-albedo, solar-reflective coatings to sidewalks and pedestrian zones in areas identified through heat vulnerability mapping. These maps combine environmental data with social indicators to prioritize interventions where needed most. Early findings show that reflective surfaces can lower pavement temperatures by up to 12 degrees Celsius, improving thermal comfort for pedestrians and reducing nearby building heat loads.
The city updates public works guidelines to include surface reflectivity as a performance standard. This shift shows how material choices, even relatively simple ones, can contribute to broader strategies for urban cooling. Athens is proving that innovative design can deliver measurable climate resilience.
Mapping Heat and Public Health in Miami, United States
Miami is approaching extreme heat as a public health issue. Led by Chief Heat Officer Jane Gilbert, the city is integrating material innovation with data analysis to identify and protect the most vulnerable communities. Its approach combines reflective coatings and expanded tree canopy coverage in neighborhoods with the highest heat exposure.
Reflective surface technologies are being tested on roads, playgrounds, and parking lots. These include solar-reflective sealants and enhanced coatings designed for durability in Miami’s humid climate. Monitoring data shows that treated surfaces stay up to 10 degrees Celsius cooler than untreated asphalt, reducing ambient temperatures in surrounding areas.
In parallel, Miami is investing in urban forestry. The city’s Urban Tree Canopy Assessment guides the planting of thousands of new trees in neighborhoods with low canopy coverage. By overlaying this map with health data, including hospital visits linked to heat-related illness, Miami is targeting interventions where they will have the most significant impact.
This combined approach links climate adaptation to public health, creating a framework prioritizing equity and measurable results. Miami is showing how cities can use material solutions to lower temperatures, reduce health risks, and improve residents’ quality of life.
Materials as Urban Climate Infrastructure
This shift in how cities understand building materials connects all of these efforts. No longer passive or neutral, materials are redefined as active tools in the fight against extreme heat. They can reflect, insulate, absorb, or deflect thermal energy. They interact with the sun, air, and water. Most importantly, they are selected not just for cost or appearance but for how well they protect people.
For designers, this denotes a challenge and an opportunity. Concepts like thermal mass, permeability, solar reflectance, and albedo are becoming as fundamental as form and function. A reflective sidewalk or a green roof may seem like an isolated detail, but when deployed at scale, these choices rewire how cities manage heat. Good materials reduce energy loads. The best ones minimize health risks and even save lives.
Toward a Heat Resilience Playbook
What we are witnessing in cities worldwide is not just a series of isolated experiments, but the early chapters of a global playbook. Each Chief Heat Officer contributes new strategies, data, and design models that expand our collective understanding of how to manage rising temperatures. These approaches vary across climate zones, cultures, and economies, but they are all united by one principle: heat is a risk that can be mitigated through design.
This work redefines materials as active climate infrastructure. Surfaces that once absorbed and stored heat are reimagined as tools for cooling and protection. Streets are no longer neutral ground; they can either harm or heal, depending on what they are made of. With better materials, cities do more than simply withstand heat—they shape it, redirect it, and reduce its impact on daily life.
For design and planning practices, the message is clear. Climate adaptation is not just about future-proofing buildings. It is about rethinking every layer of the urban fabric in terms of temperature, equity, and survival. In this emerging field, performance is measured not just in terms of energy savings or cooler spaces, but in hours of outdoor work regained, in hospital visits avoided, and in lives saved. These new metrics of success in urban design will redefine the very legacy of our cities.
This article is part of the ArchDaily Topics: Rethinking Materials: Techniques, Applications and Lifecycle, proudly presented by Sto.
Sto sponsors this topic to emphasize the importance of digitized materials in architectural design. As demonstrated in a case study with the London-based architecture firm You+Pea, its high-quality PBR-files provide architects with precise tools for confident decision-making from concept to execution. This approach bridges virtual and physical realms, supporting more accurate and efficient design.
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