The role of the existing building stock in addressing sustainable development issues receives little attention. Yet with an annual replacement rate for buildings of around 1 per cent it remains the case that the majority of buildings that will contribute either positively or negatively to sustainable development in its widest sense in the next few years are already with us. As most of them were built when sustainability was not a design issue it can be safely assumed that at present their impact is negative – it is one of the major challenges of the property industry over the next 20 years to change that impact to positive. The built environment professions must play a leading role in this reversal.