Center for the Built Environment

Designs for low-energy office buildings increasingly incorporate operable windows for the benefits of personal control, environmental quality, and architectural value. However, integrating operable windows with mechanical systems to achieve their full benefits is an unresolved energy challenge. If operable windows are left up to the control of the occupants, designers run the risk of putting unpredictable or unnecessary loads on the HVAC system, causing air pressure balancing issues, or causing unreliable or unwanted air change rates. However, if windows are automated for natural ventilation, the building design loses the comfort benefits, amenity, appeal and robustness of manually-controlled windows.

New buildings with operable windows situate themselves in an ongoing debate about the efficiency benefits of manual versus automatic building control. The decision to use manually-operated windows rests on assumptions about their value and a faith in the idea that occupants will actively participate in maintaining indoor environmental quality (compared to a conventional, sealed office environment). Concurrent with this debate, there has been growing interest in occupant behavior as the new low- hanging fruit for improving a building’s energy performance and closing the gap between predicted and actual performance. Emerging research that is relevant to these topics includes studies that better characterize and model behavior, as well as those that look at the impact of information systems and feedback on energy-using behaviors. However, these research questions are seldom considered together. This literature review draws together a number of topics that contribute to our understanding of building-occupant control interactions in mixed-mode buildings, beginning with the known (and as- yet unresolved) benefits and limits of operable windows when combined with mechanical cooling.