Building standards, regulations and labelling schemes are instruments for reducing energy demand and carbon emissions, linking policy ambitions to market-based responses. In practice, their effects are complicated. In this paper we show how ‘market standards’ in the office sector are fostering escalating energy demand and favouring building designs increasingly disconnected from changing user needs. In ‘black boxing’ ideas about needs, standards powerfully and dangerously stabilize, and often escalate, concepts of ‘normal’ provision. Far from being neutral, standards are operating amid competing interests and ambitions in the market place. Processes of black-boxing, locking-in, ratcheting, reification, circulation and disconnection (the ‘dark sides’ of standards in action) are investigated to explore how they might be avoided. The paper provides insight into the role that market standards play in energy demand in the non-domestic (office) sector, through an examination of ten case studies of speculative office developments in London.