Attention to ‘sustainability’ and energy efficiency rating schemes in the commercial property sector has increased rapidly during the past decade. In the UK, commercial properties have been certified under the BREEAM rating scheme since 1999, offering fertile ground to investigate the economic dynamics of ‘green’ certification in the commercial property market. This paper documents that, over the 2000-09 period, the expanding supply of green buildings within a given London neighbourhood had a positive impact on average rents and prices, but reduced rents and prices for environmentally certified real estate. The results suggest that there is a gentrification effect from green buildings. However, each additional "green" building decreases the marginal effect of certification in the rental and transaction markets by 2 per cent and 5 per cent respectively. In addition, controlling for lease contract features, like contract length and the rent-free period, modifies the impact of environmental certification on rental prices.