It has been estimated that over 70% of the average city's greenhouse gas emissions come from buildings. If urban buildings continue to be planned, designed, built and operated without a transformational change, the energy consumption of buildings is forecast to triple by 2050. A series of radical and integrated initiatives are needed to curb the projected growth in consumption and reduce urban dependence on fossil fuels. Sustainable buildings are not just energy-efficient; they form part of a city's positive infrastructure, contributing positively to the community and to the environment. They coexist within an integrated system and run on clean, renewable energy. They make the best use of local resources, using materials which are recycled and reused. They aim to be regenerative, actively contributing to local biodiversity and food security. They strive to adapt and evolve with climatic, economic and social change and safeguard human health and well-being. Sustainable buildings are also a celebration of both form and function. Policy and adopted practices must ensure that all these aspects are considered and actively encouraged.

It is imperative that city authorities reduce the CO2 output of existing buildings through extensive refurbishment. This may be the primary focus in more economically developed countries. They must also ensure that all new buildings aim to be carbon-neutral, or as close to it as feasibly possible. This may be the priority in less economically developed countries. Across all regions, City Hall can lead the way by tackling the public stock of buildings, and by influencing the private stock through policy and incentive schemes. In addition, city masterplans must incorporate decentralized infrastructure and green spaces, and take into account appropriate levels of urban densification. City Mayors and Governors can incentivize owners and occupiers to meet low-carbon and efficiency targets using renewable energy, and by installing water and waste management schemes. They can promote more efficient ways of occupying buildings using smart technology, and insist on building assessments at regular intervals during a building's lifespan. To help cover the costs involved in implementing such strategies, city authorities can establish business initiatives, possibly in collaboration with the private sector.

This set of knowledge cards provide examples of sustainable buildings best practice with particular focus on planning, design and operation of new and existing buildings. Please note that they are not wholly independent of energy and mobility, which are addressed in full in the two accompanying knowledge card sets.