Table of Contents
Introduction
Cities and buildings sit at the heart of the global energy and climate challenge. Most of the world’s population now lives in urban areas, and buildings account for a large share of energy use and greenhouse gas emissions. At the same time, cities concentrate people, infrastructure, money, and ideas, which makes them powerful engines for solutions. Understanding sustainable buildings and cities means seeing how design, technology, behavior, and policy interact in the places where we live and work every day.
This chapter introduces the overarching ideas that connect sustainable buildings with sustainable urban development. Detailed aspects such as green building principles, passive design, net zero buildings, heating and cooling systems, materials, urban heat islands, renewable energy in cities, mobility, planning, and nature-based solutions will all be addressed later in their own chapters. Here the focus is on why buildings and cities matter for sustainability, what makes them unsustainable today, and what a more sustainable urban future looks like in broad terms.
Why Buildings and Cities Matter for Energy and Climate
Buildings consume energy for heating, cooling, lighting, hot water, appliances, and equipment. In many countries, the building sector accounts for around a third of total final energy use. When this energy comes from fossil fuels, it leads to significant carbon dioxide emissions. Cities also depend on energy for transport, industry, and public services such as street lighting, water supply, and waste management. Urban energy use therefore plays a central role in climate change.
At the same time, cities are vulnerable to climate impacts. Heat waves, heavy rainfall, flooding, drought, and sea level rise can all disrupt buildings and infrastructure. Urban areas are often hotter than their surroundings because of the urban heat island effect, and many cities are located in coastal or riverine areas that face rising water risks. This means that building and city design must increasingly consider not only how to reduce emissions but also how to cope with a changing climate.
Population growth and urbanization amplify these pressures. As more people move to cities and demand higher living standards, the number and size of buildings grows. Without careful planning and efficient designs, this can lock in high energy use and emissions for decades. Every new building or piece of urban infrastructure will likely last many years, so choices made now matter for a long time.
The Idea of a Sustainable Building
A sustainable building aims to provide comfort, safety, and functionality while minimizing harm to the environment and promoting social and economic well-being. It is not only about using less energy, although that is important. It is also about reducing water use, improving indoor air quality, lowering waste, using materials responsibly, and supporting the health and productivity of occupants.
Conventional buildings often rely on fossil fuels for heating and cooling, have poor insulation, and waste energy through air leaks and inefficient systems. They may use materials with high embodied energy, which means a lot of energy was used to produce and transport them. They can also contribute to local problems such as air pollution and heat build-up. In contrast, sustainable buildings seek to reduce energy demand, improve efficiency, and increasingly use clean energy sources, especially renewables. They aim to do this in a way that is affordable over the building’s lifetime, not just at the moment of construction.
A key feature of sustainable buildings is life cycle thinking. This means considering the impacts of a building from the extraction of raw materials through construction, operation, maintenance, and eventual demolition or reuse. A building that is very efficient to operate but uses extremely high impact materials may still have a large overall footprint. Sustainable design tries to balance these aspects, while keeping the needs of occupants at the center.
The Idea of a Sustainable City
A sustainable city seeks to offer a high quality of life for all its residents, while keeping its environmental footprint within planetary limits and maintaining a resilient and fair society. In practice, this involves transforming how people move around, how buildings are constructed and used, how energy and resources are managed, and how land is planned and governed.
Conventional urban development often spreads outward in low density patterns, known as sprawl. This typically leads to car dependency, long commutes, higher infrastructure costs, and more energy use per person. It can also consume fertile land and disrupt natural habitats. A sustainable city, in contrast, tends toward more compact, mixed-use neighborhoods where homes, jobs, shops, and services are closer together, and where walking, cycling, and public transport are convenient and attractive.
Energy is central to this picture. A sustainable city reduces total energy demand through efficient buildings, efficient transport, and smart land use, and then supplies as much of the remaining demand as possible from renewable sources. It also manages resources such as water, waste, and materials in ways that reduce energy use and emissions. Social goals are equally important. Access to affordable housing, clean air, green spaces, and reliable energy services must extend to all groups, not only the wealthy.
Buildings within the Urban System
Individual buildings do not exist in isolation. Their performance and sustainability depend heavily on their urban context. For example, even a very efficient house located far away from jobs, schools, and services may force its residents to drive long distances. The result can be high overall energy use and emissions, despite good building design. Similarly, a skyscraper can be very efficient per square meter but may place heavy demands on electricity supply at certain times of day.
The relationship flows in the other direction as well. City-scale choices such as public transit networks, district heating and cooling systems, and land use zoning can either make sustainable buildings easier or harder to achieve. For instance, if a city invests in district energy networks, buildings can more easily connect to low carbon heat sources. If regulations set performance standards for new and existing buildings, the general level of efficiency will gradually increase.
This interdependence means that sustainable buildings and sustainable cities must be planned together. It is not enough to optimize each building on its own. Policies, design practices, and business models must consider neighborhoods and whole districts, often using integrated planning tools that bring together energy, transport, buildings, and land use.
Key Energy Concepts for Buildings and Cities
Energy use in buildings and cities can be understood through a few simple ideas that recur throughout this part of the course. One is the difference between energy demand and energy supply. Demand refers to the services people want, such as comfortable indoor temperatures, lighting levels, or kilometers of travel. Supply refers to the energy provided through electricity, fuels, or district systems to meet that demand.
A second idea is efficiency, which is the ratio of useful energy services to the primary energy consumed. If a building uses less energy to provide the same level of comfort and lighting, its efficiency has improved. In simple terms, if $E_{\text{in}}$ is the total energy supplied to a building over some period, and $E_{\text{useful}}$ is the portion that actually delivers useful services, the efficiency $\eta$ can be written as
$$\eta = \frac{E_{\text{useful}}}{E_{\text{in}}}.$$
Higher efficiency means achieving the same or better comfort and services with less energy input, which directly reduces emissions when the energy comes from fossil fuels.
A third concept is peak demand. Cities and buildings do not use the same amount of energy at all times. There are hours or seasons when demand is highest, for example hot summer afternoons or cold winter evenings. These peaks can strain electricity grids and heating systems. Sustainable buildings and cities try to lower and shift peaks, for instance through better design, storage, and smart controls, so that infrastructure can be smaller, cleaner, and more reliable.
Finally, electrification is playing a growing role in sustainable urban energy systems. Heating, hot water, and transport are increasingly provided by electric heat pumps, efficient appliances, and electric vehicles. This shifts energy use from direct fossil fuel combustion to electricity, which can then be provided by renewable sources. The success of this strategy depends on both cleaner electricity and more efficient end uses.
Linking Renewable Energy to the Built Environment
Renewable energy is essential for the long term sustainability of buildings and cities. On the supply side, cities can integrate solar, wind, geothermal, and other renewable sources into their electricity and heat systems. On the demand side, buildings and transport must be adapted to use these sources efficiently and flexibly.
In the context of buildings, rooftop solar photovoltaics, building integrated solar, and connections to off-site renewable plants are important options. At the city scale, planners can support renewables through zoning, incentives, and the design of grids and district energy networks. The availability and variability of renewable resources influence how buildings are designed, for example by encouraging better insulation and storage to cope with times when solar or wind output is low.
Sustainable urban development also involves using local renewable potential wisely. Densely built city centers have limited roof space per person, so they may rely more on regional renewable generation and highly efficient buildings. Suburban areas may offer more space for rooftop solar or small wind. The mix of renewable sources will differ among cities, depending on climate, geography, and existing infrastructure.
Resilience and Adaptation in the Urban Context
Sustainability in buildings and cities includes the ability to withstand and recover from shocks and stresses. Climate change is increasing the frequency and intensity of extreme events that test buildings and infrastructure. Heat waves can overheat poorly designed homes and offices. Storms and floods can damage structures and disrupt energy, water, and transport networks. Power outages can quickly undermine comfort and safety in modern buildings.
Resilient buildings and cities are designed and managed to reduce these risks. This can involve improving drainage systems, raising critical infrastructure above flood levels, protecting power networks, and designing buildings that stay within a tolerable temperature range during heat waves or power cuts. Green spaces and water features can help moderate temperatures and manage stormwater. Redundancy and diversity in energy sources and networks can make supply more robust.
Resilience also has a social dimension. Vulnerable populations, such as low income households or the elderly, are often the most affected by heat, cold, and disruptions. Sustainable urban strategies aim to ensure that protection and adaptation measures reach those who need them most, for example through cooling centers, affordable energy, and upgraded housing.
Social and Economic Dimensions of Sustainable Urban Development
Sustainable buildings and cities must work for people across different income levels, ages, and backgrounds. A highly efficient building that only a small wealthy group can access does not solve broader social challenges. Equally, energy saving measures that increase costs or reduce comfort for low income residents can create new injustices.
Affordability is therefore a central concern. Investments in energy efficiency and renewables can reduce energy bills over time, but they often require upfront capital. Policies and financing mechanisms are needed to support renovations and sustainable construction in social housing and modest dwellings, not only in flagship projects. Tenant and landlord relationships can also complicate decisions, because those who pay for upgrades are not always the ones who benefit from lower bills.
Jobs and local economies are another important aspect. The shift to sustainable buildings and cities creates demand for new skills in design, construction, retrofitting, maintenance, and planning. This can generate employment and business opportunities, especially if training and support are widely accessible. At the same time, workers and companies in more traditional sectors need fair pathways to adapt.
Public participation and governance have a strong influence on outcomes. Urban residents have knowledge about their neighborhoods and needs. Involving them in planning processes can lead to solutions that are better accepted and more effective. Clear rules, transparent decision making, and stable long term policies help align the many actors involved in buildings and cities, including governments, developers, utilities, engineers, architects, and citizens.
Toward Net Zero and Climate Neutral Cities
Many cities and countries are now setting targets to reach net zero greenhouse gas emissions within a few decades. Buildings and urban systems are central to these goals. A climate neutral city aims to minimize emissions from buildings, transport, industry, and waste, and to balance any remaining emissions with removals, for example through natural ecosystems or technological solutions.
In practical terms, this usually means three broad steps for buildings and cities. The first step is to reduce energy demand by improving efficiency and avoiding unnecessary consumption. The second step is to electrify as many energy uses as feasible, particularly in buildings and transport. The third step is to supply the required electricity and any remaining fuels from low carbon and renewable sources.
A common guiding principle for climate neutral buildings and cities is: “Use less energy, use energy more efficiently, and supply the remaining demand with clean and renewable sources.”
Transition pathways will vary among cities, depending on their climate, wealth, infrastructure, and political context. Historic city centers, fast growing megacities, and smaller towns all face different starting points and constraints. However, the general direction is similar, and buildings and urban planning will remain central elements of any credible net zero strategy.
Conclusion
Sustainable buildings and cities lie at the intersection of energy, environment, society, and economy. They shape how much energy we use, what kinds of energy we rely on, how resilient we are to climate impacts, and how fairly the benefits and burdens of urban life are shared. Improving their sustainability is a long term project that involves technical solutions, design choices, policies, and behavioral change.
The following chapters in this section will examine specific aspects in more detail, including green building design, passive strategies, net zero buildings, efficient systems, sustainable materials, urban heat islands, renewable energy integration in cities, mobility, planning for low carbon urban forms, and nature based solutions. Together, they will show how the broad ideas presented here can be translated into practical strategies for transforming the places where people live and work.