This paper explores the interest by policy makers to encourage and develop a green economy, with a particular focus on UK government attempts to engender a shift in the mainstream building and construction sector towards adopting green building methods and techniques. The building sector has been the focus of endeavours to engender a shift towards greener ways of working and building, due to its high contribution to greenhouse gas emissions and associated concerns over enhanced global warming and climate change. The paper outlines the recent development of national UK policy on green building as exemplified in legislation for the Code for Sustainable Homes and in Building Regulations. These have given rise to a particular set of responses to green building requirements that favour technological solutions that can readily be accommodated by the existing system. In critiquing these developments we draw upon socio-technical sustainability transitions research, one strand of which has focused on the ways in which niche developments can challenge and disrupt existing regimes of practice. We do this empirically through our research into the green building sector which has involved in-depth interviews with a range of actors from the UK green building sector, including architects, building companies, materials suppliers and policy makers. Respondents from within the green building niche are critical of current UK legislation, and argue that its narrow conceptualisation fails to adequately encourage, or recognise, what they would consider to be green building forms that will contribute to substantial reductions in carbon emissions, nor does it respect locally appropriate building methods. (C) 2014 Elsevier Ltd. All rights reserved.