This paper examines the incorporation of carbon data into the Building Information Model (BIM) process and considers option appraisals that will enable design team members to evaluate both operational and embodied CO2 emissions over the life cycle of a project. The paper is based upon work, funded by the Technology Strategy Board, to develop a toolkit that utilises interoperable standards around a BIM. This allows for architects, energy advisors and others to develop and share design information on CO2 emissions whilst each design team member is free to use their own preferred software solution. At the core of the process is a three-dimensional BIM with links to elemental, system and material databases. The work on the model is described along with its application to a case study on a recently completed new school, built to sustainable standards in the North East of England.