In recent decades there has been growing awareness of the environmental impact of man’s activities, and concerted efforts to identify and address the key factors that give rise to the most damaging impacts. It has become clear that buildings are one of the principal sources of environmental degradation. This is primarily due to the carbon impact of the fossil fuels used to operate buildings, which is a major contributor to climate change. There is an imperative for those practising as building services designers to influence the design of buildings, and to plan their active engineering systems, so that carbon emissions are minimised. This requires an awareness of all the factors that give rise to carbon emissions throughout the life cycle of a building.