Buildings are currently responsible for 32% of global energy consumption and one-quarter of global human-induced CO2 emissions, according to the World Resources Institute (WRI). But the built environment also has the greatest economic potential for carbon dioxide emission mitigation compared to other sectors.

The WRI released its Building Efficiency Accelerator (BEA) program to provide a guide for leaders in public and private sectors to follow in order to increase building efficiency and reach sustainability goals in their cities. “The BEA partnership brings technical experts together with local governments to improve policies, deliver more efficient buildings and technologies, and transform cities,” says Jennifer Layke, global director of WRI’s energy program. “Energy efficient buildings create environmental, health and economic benefits.”

These seven sustainable cities have committed to and made progress toward increasing the efficiency of their buildings and urban development projects, securing their ranking on the list of the world’s most sustainable cities.

Bogotá was selected to drive building efficiency and sustainable cities across the globe through the BEA program in 2016. In preparation for the 18 million Colombians that are expected to move to cities by 2050, the country has been working to maximize land use and energy efficiency, especially in urban areas like Bogotá.

“We want the city to be as compact as possible, but also to be adaptive to climate change and as low as it can be in terms of consumption,” says Cristina Gamboa, director and CEO of the Colombia Green Building Council (Consejo Colombiano de Construcción Sostenible, CCCS).

Since 2009, the CCCS has been part of the World Green Building Council, with Bogota as one of 30 world cities involved in the BEA program. Bogota is in the midst of drafting a new master plan for the next 12 years to improve quality of life in the city, with a goal of reducing greenhouse gas emissions by 32% in new buildings.

Buildings like the Elementos—four LEED Platinum towers on Avenue 26—are an example of what can be done with recycled content, solar panels, a green roof, low-emitting materials, and countless other sustainable building features. Certified in 2017, this project allowed for 67% savings in water and 48% in energy overall, and it’s 100% naturally ventilated.

On the same street you’ll find the T7/T8 Business Tower, LEED Gold certified in 2017. Sustainable building strategies and a careful selection of lights, faucets, and other equipment resulted in a savings of 15% energy and 38% water, compared to traditional offices. The tower was built with 28% recycled materials—44% of which come from the region.

There is a history of resourceful architecture in Bogotá. Colombians have long built using simple resources and simple techniques, focusing on reusing and reshaping things, says Daniel Bonilla of Daniel Bonilla Arquitectos and design director of TAB, or Taller de Arquitectura de Bogotá (Bogotá Architecture Workshop).

Bogota is increasingly looking at establishing and fine-tuning public policy that flags buildings as a priority for reducing greenhouse gas emissions. This commitment has changed how all new construction projects are approached, from renovating the historic, mountainous foot path to Monserrate to building schools and libraries as a way to invest in better education to promoting eco-tourism through sustainably designed restaurants, hotels, and businesses.

At the same time urban populations are predicted to increase, Boston has committed to being carbon neutral by 2050. Austin Blackmon, chief of Environment, Energy & Open Space, says Boston is actively pursuing initiatives aimed at engaging residents and promoting sustainability, and it has been paying off. In 2017, The American Council for an Energy-Efficient Economy recognized Boston as the most energy-efficient city in the U.S. In the same year, USGBC named Massachusetts the number one state for LEED projects for the second year in a row, with a total of 130 projects.

As the city faces increased flood risks and other effects of climate change, Blackmon says one of their priorities is Climate Ready Boston, a program that assesses the city’s vulnerability and outlines goals—from developing local climate resilience plans to creating a coastal protection system to address flood risk. It details actions big and small, like having an expanded urban tree canopy and a protective, floodable waterfront park. Meanwhile, Renew Boston encourages residents and small businesses to become more energy efficient, too.

From green renovations to eco-friendly construction projects, development in Boston has become increasingly sustainable. The Boston Public Library underwent renovations completed by William Rawn Associates in July 2016 that incorporated a number of energy-efficient features. Insulated ultra clear glass replaced the dark tinted single pane original glazing to address the lack of natural lighting and reduce the need for as many light fixtures. Lights were replaced with LED fixtures to further efficiency, while removing dividing walls and making the two-story space invited more balanced natural light from multiple directions.

Low-flow plumbing fixtures and non-electric flushometers were installed in new and existing toilet rooms. The design also included occupancy sensors and improved controls, and CAV (Constant Air Volume) boxes were replaced with VAV (Variable Air Volume) boxes to reduce energy and conditioned air usage. Unlike CAV systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant temperature.

Construction continues on the GE Innovation Point campus in Boston, another development project that began in May 2017. The design incorporates green technology while leaving room for future innovation. Gensler, the architecture firm behind the design, aims to generate approximately 10% of the campus’ energy use from a solar veil with easily removable photovoltaic panels to ensure generation capabilities can advance in the future.

The flexible framework of the veil will also shade the southern façade to reduce solar heat gain and glare. In addition, Innovation Point will include rooftop gardens and outdoor spaces, water recapture and reuse systems, and charging stations for electric vehicles.

Boston’s neighborhoods are also beginning to build houses prioritizing energy efficiency in their design. In Wellesley, about 16 miles from Boston, ZeroEnergy Design built a house that includes an impressive array of solar panels, and top building enclosure strategies, such as continuous insulation, an airtight envelope, and triple-pane high-performance windows.

The house also features efficient HVAC systems, including an air source heat pump for heating and cooling, a heat pump hot water heater, LED lighting, energy recovery ventilation, high efficiency appliances, and more. This house is an innovative example of building for more sustainable cities without sacrificing comfort and style, with energy performance, thermal comfort, and indoor air quality in mind.

The capital of Norway is also one of the most sustainable cities. The city welcomes 10,000 new residents each year, bringing in a flood of green developers and architects ready to tackle sustainability in a growing city. Eco-friendly initiatives are on the rise, like the mandate that requires all new municipality-built buildings be not only zero-emission, but to also be “energy-plus,” actually generating energy.

Oslo aims to be climate-neutral by 2030. Emissions are being tracked citywide, the municipal pension fund is invested in green projects instead of fossil fuel-based projects, and the city aims to have a car-free city center. Oslo even offers incentives like tax credits, access to public transport lanes, and waived tolls to anyone driving electric cars, plus credits for electric transport bicycles. With all of these exciting prospects in long-term sustainability and more on the way, Oslo and its 660,000 people have proved they are all in on sustainable building, which is why programs like FutureBuilt have been so successful.

FutureBuilt is a 10-year program that identifies green pilot projects in an effort to develop carbon neutral sustainable cities and impressive architecture. The program’s goal of 50 completed pilot projects by 2020, all of which have to have a carbon footprint 50% lower than business as usual, will likely be exceeded soon, as the number surpassed 45 in January 2018.

The program looks at three areas—energy in use, the embodied energy in building materials, and mobility, including where a project is located and how it’s served (i.e. bicycles, parking, and public transportation). As the program nears its 2020 deadline, the process to become a FutureBuilt project has become stricter, requiring nearly zero-energy or plus-energy status.

This city-wide drive for sustainable building is reshaping entire neighborhoods. The Vulkan area between Oslo’s city center and the Grünerløkka borough was developed along the scenic Akerselva river walk. This bustling area is now home to two Energy Class A hotels, an uber popular food hall, the country’s largest charging facility for electric cars, and a plethora of restaurants and bars.

A system of geothermal wells that runs nearly 1,000 feet deep supplies all of Vulkan’s buildings with heating and cooling. Extensive solar water heating systems, state-of-the-art insulation solutions, and recycling energy from coolers and elevators are all found in the city’s buildings, and it’s making a difference to Oslo’s growing legacy as one of the top sustainable cities worldwide.

Not only is London one of the most sustainable cities in the world, but it also seeks to become the world’s first National Park City, with a goal of being zero-carbon by 2050. The city strives to reduce greenhouse gas emissions by at least 60% by 2025—encouraging architects and builders to think along the same lines.

The potential new title reflects on how urban and environmental aspects of London often combine. Famous urban sites intertwine with more than 35,000 acres of public green spaces maintained by the city—40% of its entire area. There are more than 700 green roofs in central London alone, and it is also home to one of the most sustainable mass transport systems in the world. In 2003, city officials introduced the transit tax to encourage use of public transport and reduce car emissions.

The buildings are beginning to reflect this duality. The cancer center Maggie's Centre Barts, for instance, has a glass design that minimized solar gain while maximizing the amount of natural light. The world’s largest building constructed out of cross-laminated timber, Dalston Works, is also in London.

Bloomberg’s new European headquarters, completed in 2017 in the heart of London, earned a 98.5% BREEAM rating, the highest score for an office building to date. The “breathable” walls open and close based on weather conditions, resulting in a reduced dependency on mechanical ventilation and cooling equipment. Aluminum ceiling tiles assist in the heating, cooling, lighting, and acoustics of the building. Rather than using a traditional office fluorescent light system, the building has 500,000 LED lights—using 40% less energy.

The Bloomberg building uses an estimated 73% less water than the typical office building. An on-site Combined Heat and Power generation center supplies heat and power in a single efficient system, estimated to reduce energy consumption by 35%.

The Bloomberg building is also a zero-landfill facility—and has been since construction began in 2010. Instead of going to the landfill, waste is composted or converted to energy. The workplace uses a waste system that allows a greater proportion to be recycled. All of these innovations are paving the way for green developments in sustainable cities, and future National Park Cities, across the world.

Home to 6.5 million people and one of the fastest growing provinces in the country, the Western Cape of South Africa is already being heavily impacted by the effects of climate change. The crippling droughts, electricity insecurities, and rising costs are simultaneously concerning and mobilizing the people of the region, and Cape Town is leading the way in the sustainable cities movement.

South Africa is poised to become a global green building leader by 2019, with Cape Town vying for a position at the heart of that transformation, according to the Dodge Data SmartMarket World Green Building Trends Report 2016. This is most clearly demonstrated through the large sustainable development projects popping up in the South African city.

No single area is more symbolic of the transformation bubbling over in the Western cape than the bustling V&A Waterfront, a mixed-use sustainable development encompassing more than 300 acres of residential and commercial buildings. More than 21,000 people work there, 1,500 live there, and as many as 180,000 visit daily. While the V&A Waterfront plays an important role in the economy of the area, it also plays an even more important role in the fight to preserve resources.

One of the green projects at the Waterfront is the Zeitz Museum of Contemporary Art Africa (Zeitz MOCAA), which opened in September 2017 and is housed in a converted historical grain silo. Developers had to find innovative ways to preserve and acknowledge the building’s history while recycling and reusing material, minimizing the carbon footprint, and still giving it a new, contemporary use, essentially “reverse-engineering” sustainability into the property.

The Radisson RED Hotel is another V&A Waterfront project focused on sustainability, and it opened in the same area around the same time as the Zeitz MOCAA,. In the design and build phase, the V&A implemented key green elements that reduced the building’s strain on resources (via the central seawater cooling system, spatially efficient design that makes use of daylight, and lighter wall thickness). Within the hotel, food waste has been reduced by more than 30%, and there is a “no paper” policy in the studio rooms.

Other innovations implemented within the waterfront area include efficient water and electrical design to minimize demand on resources, water and energy metering systems to manage consumption, efficient use of space using light-weight internal walls to reduce wall thickness and decrease total building weight, and using low-VOC finishes and natural lighting. The area also incorporates durable yet cost-effective building facades that could withstand the harsh harbor environment and offer thermal performance, and an impressive cooling system that uses cold Atlantic seawater from the harbor to regulate internal building temperatures and eliminate the need for air-conditioning and other cooling systems.

Melbourne has repeatedly been named the world’s most livable city, according to the Economist’s Global Liveability Report 2017. The criteria used for this ranking system evaluates a multitude of factors related to stability, health care, culture/environment, education, and infrastructure, so it’s no surprise Melbourne is also gunning for a spot on the list of the world’s most sustainable cities.

In 2003, the city announced its goal to achieve net zero emissions by 2020, and there is a huge push to increase renewable energy use even sooner. With 78% of the municipality’s greenhouse gas emissions generated by existing buildings, Melbourne has focused its energy (literally) on renovating and retrofitting old buildings to become increasingly energy efficient.

This effort has been supported by programs like the 1200 Buildings retrofit program, the commercial office program CitySwitch, and the residential apartment program Smart Blocks, in which the city provides building owners and tenants access to financial incentives and grants to help existing buildings increase their uptake of energy efficiency and renewable energy solutions.

Since 2010, the owners of more than 540 commercial office buildings in Melbourne have retrofitted to improve energy and water efficiency.

One of the most impressive examples to date is the renovation of the fourth tallest building in Australia: 101 Collins. Since it was built in the 1990s, the owners wanted to improve sustainability in the building, specifically in regards to energy efficiency, leading to an installation of 180 photovoltaic solar panels on the 56th floor of the building. It’s the largest and tallest private commercial solar PV installation in Melbourne.

The panels generate 47,000 kWh of electricity per year, or more than the annual amount of electricity used in more than 12 houses. This sustainable building also has LED and motion sensor lighting, new high efficiency VSD chillers, an upgraded BMS, and double glazed windows with surface coated tempered glass to increase thermal efficiency.

Over the last decade, Seattle has been ranked the fastest growing big city in the U.S., a title that does not immediately suggest that the Pacific Northwest city is one of the most sustainable cities across the globe. However, Seattle reached “peak emissions” in 2008, and emissions have been on a downward trend ever since the city committed to creating a more eco-friendly environment, according to Seattle’s Environmental Progress Report 2017.

Seattle aims to reduce total core greenhouse gas emissions 58% by 2030 and become carbon neutral by 2050, with a 91% reduction in passenger vehicle and building energy emissions, compared with their 2008 emission levels, all while the population continues to increase. The result is an explosion of green development to keep things in the balance.

One project that exemplifies the development expansion in Seattle is the 208,000-square-foot technology office space called NorthEdge, home to the data visualization company, Tableau. The building itself is stacked along the grade of its hillslope, with the hillside acting as a watershed with underground water heading to nearby Lake Union, so maintaining the integrity of the watershed was a vital part of the design.

The LEED Silver–certified design mainly focused on water and water management, with a 57% reduction in landscaping use and a 35% reduction in potable water use.

While the buildings of major companies often steal the spotlight in Seattle, green design is booming all over the city, even in places that have historically struggled with economic and gang-related challenges, such as the Central Tacoma and Hilltop neighborhoods where Bates Technical College built a LEED Gold–certified technology center.

The sustainable features of the Bates College Advanced Technology Center include a green roof that captures rainwater runoff, while a ground source heat exchanger and heat recovery from the server tower offer an estimated 35% reduction in energy use, saving nearly $25,000. Irrigation and domestic water use reduction features also save hundreds of gallons of water each year.