Methods for the environmental assessment and certification of green' buildings are increasingly being adopted by local governments and other entities as a means of meeting environmental, and often energy-related, goals. Literature on building environmental assessment has examined how these tools are interpreted by stakeholders in design and construction, but less attention has been paid to their interpretation and usage as objects of policy - despite this being a channel through which they have a potentially huge impact. Based on a case study of the emergence of green building in Israel, and drawing on socio-technical literatures, this paper explores the meanings attributed to building environmental assessment in the policy context. It finds that these meanings include a platform for divergent environmental goals and a proxy measure for greenhouse gas abatement. The analysis suggests that for policy-makers, the significance of green building lies not in its constituting a set of environmental benchmarks but as a standard that gains currency as a black-boxed policy object. An open discussion is needed on the various logics driving the use of green building tools in public policy, and what they hope to achieve.