Global Warming and Cities: How Architecture Can Respond to Urban Heat

At MJARC Arquitetos, we believe that today’s decisions dictate tomorrow’s future. Good planning and integrated solutions are not an optional extra — they are an indispensable condition for mitigating climate change and ensuring a better future for those who will inhabit, work, and live in the spaces we design.

Global warming is no longer a distant prediction. It is present in the way we inhabit cities: in streets too hot to walk on, in homes that trap heat overnight, in unshaded plazas, in rising energy consumption, and in the difficulty of remaining in public spaces during extreme heat events.

In recent days, Europe has once again faced severe heatwaves. Barcelona recorded 40.7 ºC, its highest temperature in 112 years, while other parts of Spain reached values close to 44 ºC. In the United Kingdom, health alerts were issued due to the heat, with particular concern for children, the elderly, and vulnerable populations. France, Italy, Ireland, and other European regions also faced high-temperature warnings.

These events highlight an essential issue: cities do not heat up solely because of air temperature; they also heat up because of how they are built.

An excess of asphalt, concrete, impermeable surfaces, exposed facades, dark roofs, and a lack of vegetation contributes to the so-called urban heat island effect — a phenomenon where urbanized areas accumulate and release more heat than natural or less-built environments.

Faced with this reality, architecture cannot limit itself to designing isolated buildings. It must respond to microclimates, shade, soil, water, ventilation, materials, and the presence of nature — the same integrated approach we apply to every architecture and urbanism project.

Urban heat is already changing life in cities

Heatwaves are no longer exceptional occurrences. According to data from the European Copernicus service, Western Europe recorded its hottest June on record, with temperatures significantly above recent averages. The increasing frequency and intensity of these episodes are also linked to greater pressure on public health, wildfire risks, nocturnal discomfort, and higher energy consumption.

The problem extends beyond mere discomfort. Overheated cities impact:

• Public health, particularly for vulnerable individuals;

• Mobility, as walking or waiting in exposed areas becomes difficult;

• Public life, when squares and streets cease to be places of community gathering;

• Housing, especially in poorly oriented or inadequately insulated buildings;

• Energy consumption, driven by an increased reliance on air conditioning;

• The urban economy, as commerce, tourism, transportation, and services are also disrupted.

Even transport infrastructure is being re-evaluated for extreme heat scenarios. Eurostar, for instance, updated the specifications for its new trains to operate in temperatures up to 55 ºC, anticipating harsher European summers over the coming decades.

The lesson for architecture is clear: designing based on past climate conditions is no longer sufficient. Homes, hotels, schools, streets, and public spaces must be conceived for a warmer, more volatile, and more demanding climate.

More air conditioning does not solve the problem

The immediate reaction to heat is often to install or increase the use of air conditioning. In certain contexts, mechanical cooling is necessary. However, when a city and its buildings rely solely on mechanical solutions, the problem is merely shifted, not solved.

Air conditioning cools indoor environments but increases energy consumption and expels heat back outside. While it may improve comfort inside a building, it contributes to worsening urban discomfort outdoors.

At MJARC, employing passive solutions — which do not require mechanical equipment — is mandatory and should always serve as the primary response; mechanical systems should be the exception, not the rule. Architecture must intervene before machinery is introduced.

A well-designed building can significantly reduce cooling demands through strategic decisions such as:

• Proper site placement and solar orientation;

• Window shading and exterior solar protection;

• Natural ventilation and high-efficiency insulation;

• Thoughtful selection of materials and integration of greenery;

• A seamless relationship between indoor and outdoor spaces.

Thermal comfort begins long before equipment is installed. It starts on the drawing board. We detail these strategies at the residential scale in our article Make your home efficient and reduce energy consumption.

Architectural response strategies to urban heat

1. Shade: an essential infrastructure

For a long time, shade was treated as an afterthought: a secondary byproduct of trees, balconies, overhangs, or structures. Today, in a warmer city, shade must be understood as infrastructure.

A street without shade becomes unwalkable. An exposed plaza loses its function as a gathering place. An unprotected facade absorbs excessive heat. An unshaded urban path becomes hostile to pedestrians.

Architecture can contribute through well-proportioned balconies and eaves, exterior arcades, pergolas and lightweight structures, deep-set facades, shaded courtyards, trees integrated into urban design, and carefully planned indoor-outdoor transitions. Shade should not be tacked on at the end of a project — it must be part of its fundamental logic from day one.

Green View Tower Project

2. Vegetation: more than just decoration

Vegetation is not merely a decorative element. In an urban setting, it functions as a thermal, environmental, and sensory regulation tool. Trees, gardens, green roofs, living facades, and planted zones help generate shade, reduce surface temperatures, foster biodiversity, and improve outdoor comfort.

A notable example is Paris’s OASIS program, which converts schoolyards into cooler, more resilient spaces. The strategy focuses on removing impermeable surfaces, introducing vegetation, creating shaded areas, and testing alternative materials to mitigate the heat island effect. Studies on the program identified schools with high potential for urban cooling and evaluated the thermal performance of green, bio-sourced, recycled, and reflective pavements during heatwave conditions.

This example demonstrates that even seemingly secondary spaces — such as school grounds, backyards, or building perimeters — can become active climate control assets.

In our approach, nature is not added as an after-thought; it forms part of the project’s structural backbone. Existing trees, topography, soil, shade, views, and plant species inform the architecture from our very first reading of the site.

3. The ground needs to breathe

A significant portion of urban heat is directly tied to how we treat the ground. Impermeable surfaces trap heat, prevent stormwater infiltration, and increase surface runoff during heavy rainfall. A city better prepared for heat needs to restore permeability to the land through:

• Draining pavements and landscaped green zones;

• Reduction of hardscapes and creation of permeable courtyards;

• Green roofs and rainwater retention and infiltration systems;

• Greater continuity across green corridors.

So-called cool pavements — designed to lower the thermal contribution of urban surfaces — include reflective, vegetated, evaporative, permeable, or high-capacity temperature-regulating options. Technical literature indicates, however, that there is no universal solution: performance depends on material composition, solar radiation, shade, maintenance, and urban context.

Source: https://alemdainercia.com/2025/05/01/permeabilidade-do-pavimento-intertravado-beneficios-para-a-drenagem-urbana/

This is highly relevant to architecture because paving choices are never neutral. Choosing asphalt, stone, concrete, stabilized gravel, permeable paving, or planted lawn simultaneously impacts heat, drainage, maintenance, and user experience.

4. Materials, facades, and roofs matter

Materials heavily dictate how buildings and outdoor spaces absorb, reflect, and release heat. Extremely dark or exposed surfaces can reach elevated temperatures. Unshaded glass facades increase solar heat gains. Poorly planned roofing can turn into large heat-storing surfaces.

Therefore, material selection must consider thermal behavior, durability, maintenance, sun exposure, color, albedo/reflectance, thermal mass, environmental footprint, and aging performance.

Green roofs offer a compelling response when aligned with the project’s design intent, as they help enhance thermal performance, retain rainwater, foster urban biodiversity, and lower surface temperatures. However, they require careful technical planning, maintenance, plant species selection, and structural integration.

At MJARC, this reflection is embedded in projects where roofing, vegetation, and site integration are not mere aesthetic choices, but part of how the building anchors itself to the land — principles we elaborate on in our article on sustainable buildings and architectural considerations, exploring solar control, thermal management, and passive cooling strategies.

5. Natural ventilation and passive design

Natural ventilation remains one of the most effective strategies for enhancing thermal comfort, particularly when incorporated from the inception of the design. Window placement, cross-ventilation potential, ceiling heights, internal courtyards, solar shading, and the relationship between cool and exposed zones can dramatically alter how a building reacts to heat.

Key passive strategies include cross-ventilation, internal courtyards, exterior shading, window solar protection, optimal building orientation, high-performance insulation, strategic thermal mass, solar heat gain reduction, and placing vegetation adjacent to living areas.

Cicioso Boutique Hotel Project

While these strategies do not entirely eliminate the need for mechanical systems in all climates, they dramatically lower energy dependence and elevate indoor environment quality.

Real-world urban adaptation examples

Cities around the world are actively testing climate adaptation strategies:

• Paris (France): The OASIS schoolyard initiative illustrates how existing sites can be repurposed into cool islands using vegetation, shade, alternative materials, and unpaved ground.

• Rotterdam (Netherlands): Climate adaptation is driven by a “blue-green” strategy featuring green roofs, water retention plazas, public space equipped for extreme weather events, and stormwater-integrated urban design. The city actively promotes green roofs and increased water storage capacity requirements per square meter of roof, easing pressure on drainage networks during heavy downpours.

These examples confirm that responding to global warming goes beyond cooling individual buildings — it demands rethinking the entire relationship between architecture, soil, water, shade, and nature.

The MJARC Arquitetos perspective

We believe responding to global warming begins with a deep reading of the site. Every project must understand its climate, topography, solar path, wind patterns, existing vegetation, materials, and how occupants will inhabit the space over time.

Sustainability should not be treated as a final coat of paint, a badge, or an isolated marketing statement. It must be woven into fundamental project decisions: site placement, orientation, ground preservation, shade generation, material selection, and contextual belonging. This integrated approach underpins our practice as a studio with LEED certification, embedding clear, measurable urban heat mitigation criteria into the earliest design phases of every project.

In an era of warming cities, architecture bears the responsibility of delivering more comfortable, permeable, green, and future-ready spaces. Building with climate awareness means designing places that do not merely withstand heat, but make living more humane and viable.

If you are planning a new project or rehabilitating an existing building and want to explore how these strategies apply to your specific context, contact our team.

Frequently asked questions about urban heat and architecture

• What is the urban heat island effect? It is a phenomenon where urban areas accumulate significantly more heat than surrounding natural or less developed environments due to materials like asphalt and concrete, lack of vegetation, soil sealing, and built density.
• Can architecture reduce urban heat? Yes. Architecture mitigates urban heat through shading, natural ventilation, appropriate material selection, urban greenery, green roofs, permeable paving, and bioclimatic design principles.
• Why do some houses get excessively hot in summer? Many homes overheat due to poor solar orientation, unshaded windows, insufficient insulation, restricted cross-ventilation, dark/heat-absorbing materials, or a lack of passive cooling strategies.
• Does vegetation genuinely help cool spaces? Absolutely. Vegetation casts shade, lowers surface temperatures via evapotranspiration, enhances outdoor microclimates, supports biodiversity, and regulates soil-water-temperature relationships.

Sources and references

• The Guardian: European heatwave coverage (Barcelona, Spain, UK, France, Italy, and Ireland) and Copernicus data regarding the hottest June on record in Western Europe.
• Financial Times: Technical adaptations of new Eurostar train fleets to operate in temperatures up to 55 ºC.
• OASIS Program (Paris): Thermal and microclimate studies evaluating alternative paving materials in schoolyards.
• Cool Pavements Technical Review: Reflective and permeable pavement technologies for urban heat mitigation.
• Rotterdam Strategy Reports: Green roof initiatives and urban rainwater retention regulations.