With the increasing interest in grid-interactive efficient buildings, energy storage technologies are being re-evaluated for their role in the future grid. Ice thermal energy storage (ITS) has a large potential to provide load flexibility to a grid dominated by variable generation assets, but it requires careful design, analysis, and control to be effective. Evaluation is possible using building energy simulations, but is not often done because of the complexity and added effort required to include ice storage in building simulation models. The objectives of this study are two-fold: (1) automate the addition of ice energy storage to building models through OpenStudio measure scripting and (2) evaluate the load flexibility potential of example ITS design and control strategies. This paper presents a new OpenStudio measure that provides the ability to easily and accurately model a variety of potential design options and common control schemes. After applying this measure, we then bound the ability of the building to increase or decrease its predicted future electric load over 30-minute to 6-hour windows using chiller and ice storage performance constraints at each simulation timestep. Finally, we evaluate the ITS performance against in-simulation demand response events.