Urban development is one of the main ways that human beings impact the earth. From the structures that we call home, to our schools, hospitals, workplaces and the infrastructure that we travel on, our built world now accounts for a significant portion of all greenhouse gas emissions produced worldwide. From initiatives to make entire cities carbon-neutral to innovations in concrete manufacture and even smog-eating buildings, the construction industry is beginning to recognize its role and respond, but much more needs to be done and at a faster rate. To make a real difference we must reach beyond the construction sector and enable each and every one of us to better understand how our buildings are impacting the planet. Technology can play a key role here, particularly in the form of the digital twin systems that have supported other sectors for many years. Creating a digital replica of a physical building that actually behaves like the real structure and provides crucial information on real life performance can enable us to better understand how our buildings are performing and simulate how they may perform in the future under a range of scenarios. Leveraging artificial intelligence and machine learning, these so-called digital twins can improve energy resilience, reduce operating costs, increase resource efficiency, and help to de-carbonize our buildings.