The built environment is an important contributor to global carbon emissions—in Europe, for example, buildings account for 40% of total energy consumption. Buildings need to be designed to be energy efficient to help address the climate emergency. It is not enough to design individual buildings that are attuned to their environment and climate, and thus need less energy. We must also design and assemble our built environment in a compact way that reduces our dependence on fossil fuels and promotes individual and planetary health and wellbeing. If we live close to our work and school, we can walk or cycle rather than driving, which has benefits for both physical and psychological health. It is important to note that countries and communities that are least responsible for climate change (e.g. use less energy) are feeling the impact of the decisions made on the opposite side of the world. The design of the built environment has an important role to play in climate justice. This session introduces children to energy efficiency in the built environment and invites them to contribute to solutions with their own design ideas.