How can an understanding of carbon markets assist decision making for energy efficient buildings?  --The built environment has an essential role to play in the transition to a low-carbon economy envisaged in the Kyoto Protocol: buildings typically account for one-third to one half of all emissions in developed countries.  As yet, however, market-based tools have had little impact on the construction professions.  --Market-based mechanisms are increasing in importance as policy tools in the field of energy efficiency.  This presentation provides an overview of trading experience in markets for carbon and other pollutants: examples include the RECLAIM market in Southern California, UK emissions trading scheme and forthcoming EU-wide trading market.  It uses case study examples of building projects in California to illustrate the potential for market-based mechanisms in this field.