Buildings are some of the biggest users of materials and water, consume nearly half of the world’s energy, and contribute almost half of global greenhouse gas emissions. With more buildings sprouting up every year and existing ones often being inefficient, cities have begun to tap into their toolkit of policies to help reach sustainability goals.

Four Methods That Work

Tapping into their policy toolkits, municipalities around the world are using a blend of building codes and permits, zoning regulations, building performance ordinances, and other mandates and regulations. Taxes and other financial policies can provide additional incentives. Subsidies can reduce the upfront cost of retrofits and ensure that lower-income residents are not left behind.

Here are four tactics that cities and their residents are using to push toward urban sustainability:

1. Building Certifications

Hundreds of green certifications exist today, ranging from standards for equipment and appliances (such as Energy Star and WaterSense) to certifications for entire buildings (such as BREEAM and LEED). These rating systems vary in ambition and are often adapted to local factors. In the water-scarce Middle East, for example, the United Arab Emirates’ Estidama system weights water efficiency very heavily compared to other major certifications. The Living Building Challenge available in the United States and Canada is more ambitious than most rating systems: to gain certification, a building must generate all of its own electricity and use only water collected on site.

2. Building Codes

Building certifications are sometimes time-consuming and costly. But cities can set their own standards by creating new building codes and revisiting outdated ones. Like certifications, codes can be voluntary or mandatory. Copenhagen, Denmark, requires that new buildings have “nearly zero” net energy consumption by 2020. In Singapore, the Building Control Act enacted in 2008 aims to have at least 80 percent of new and existing buildings meet green standards by 2030. And France mandated in 2015 that all new commercial buildings must be partially covered with either a green roof or solar panels.

3. Technology Mandates and Ordinances

Cities in China, Brazil, and Spain have been leading efforts to integrate solar thermal technologies into buildings. These solar water heaters do not require burdensome national or state government approval (they don’t face the same levels of permitting as, say, rooftop solar power) and are therefore easier for local authorities to implement. Combined with product certification standards to avoid the proliferation of low-quality equipment, technology-specific mandates are shifting urban energy consumption across entire cities.

4. Green Social Housing

Cities can directly get involved in promoting sustainable buildings by integrating them with their efforts to provide social housing and improve local infrastructure. Green building and affordable housing are a logical fit, as efficient designs represent long-term savings for residents who are already struggling financially. In Europe, energy-efficient building designs and the use of renewable energy-based district heating systems can help the estimated 50 million to 125 million residents who are “fuel poor,” meaning that they spend more than 10 percent of their household income on heating fuel to stay warm.