The ultimate aim of sustainability in buildings gained an additional new dimension as the start of the year 2020 saw a rapid worldwide spread of the infectious disease caused by a coronavirus named COVID-19. There is evidence that, in addition to person to person contact, the disease transmission occurs through airborne droplets/aerosols generated by breathing, speaking, coughing or sneezing. For that reason, building heating, ventilating and air conditioning systems can play an important role, as they may both contribute as well as reduce the transmission risk. However, there is insufficient understanding of the movement of infectious aerosols in buildings. This article introduces a method of bottom-up emergent modelling of the movement of infectious aerosols in internal space using a physics engine, and reports on simple simulation experiments. The results show that the smallest droplets that are large enough to contain the virus can be suspended in the air for an extended period of time; that turbulent air flow can contribute to the infectious aerosols remaining in the room; and that unidirectional air flow can contribute to purging the room of the infectious aerosols. The model introduced in this article is a starting point for further development and for increasing our understanding of the movement of infectious aerosols in buildings, and thus for increased sustainability of building design.