Switchable ethylene-tetrafluoroethylene (ETFE) cushions with kinetic shading mechanisms are increasingly being used in building enclosures to dynamically control the transmission of solar and visible light. While buildings with switchable ETFE fa?ades typically utilize simple Rule-Based logic to control their operation, this study uses a novel co-simulation approach to optimize the operation of switchable ETFE fa?ades on two hypothetical office buildings in Chicago, IL. Four seasonally representative simulation days are used to demonstrate the approach. The daily source energy savings potential of the Optimal Control schedule is up to 8.2%, 11.1%, and 25.5% compared to Rule-Based, Always-Dark, and Always-Bright control strategies, respectively.