Recent technical guidance has suggested that comfort and energy efficiency should not be seen as mutually exclusive [CIBSE, "TM54: Evaluating operational energy performance of buildings at the design stage", 2013]. Currently, however, there is a lack of comprehensive understanding of energy use during building operation and how it influences user comfort. Through comparison of the complex relationships between energy, thermal comfort, and environmental strategy in two flexible higher-education buildings in Sheffield, this paper demonstrates how designers can utilise aspects of active and passive design to deliver more comfortable, lower-energy workspaces. Analysis of the authors' post-occupancy evaluation of each case study examines what lessons might be learnt and applied to other institutional buildings in order to save energy without compromising occupant comfort. The findings illustrate how perceptions of comfort can be improved by increasing the degree of environmental control occupants have without necessarily increasing energy consumption. The paper highlights the significance of occupancy patterns to a complete understanding of energy efficiency and comfort, and speculates that the prediction and assessment of energy per occupant may have an important future role to play in bridging the gap between energy performance and comfort. (C) 2016 Elsevier B.V. All rights reserved.