IntroductionThe modern healthcare system is under growing pressure to improve the quality and reduce the cost of care (Hamilton, 2009; DHHS, 2011). Healthcare clients require design solutions that contribute to efficient operations, improved patient outcomes, and optimum building performance. Simulation and mock-up tools can be used to streamline design decisions and integrate emerging technologies and processes prior to the occupancy of a facility. Simulations have the added advantage of being able to secure a wellinformed commitment from key stakeholders and potential investors earlier in project delivery. These benefits, in addition to the ability to testdrive design ideas before they are constructed, have made simulations and mock-ups a growing trend in the research of built environments.The aim of this column is to provide an introduction to simulation and mock-up research methods that can be used to inform and optimize building design. Every simulation is based on an underlying model and represents an activation of that model over space and time. A model is a representation of a real-world system; it is a simplified abstraction of a system with a set of input assumptions. For example, a mock-up of a patient room is a type of simulation model that can be used to run simulations and thereby draw conclusions about the real system of a patient room.In general, simulation models provide a test environment that can be used for training, education, and testing the efficacy of design solutions in a controlled environment. Mock-ups and other forms of experience-based simulations are consistently used in the military, aviation, court rooms, medicine, education, and clinical psychology (Maldovan, Messner, & Faddoul, 2006; Scerbo, Bliss, Schmidt, & Thompson, 2006; Youngblood et al., 2008). Computer-based simulations are frequently used in manufacturing to streamline systems (Kibira & McLean, 2002).Although simulation techniques have a wide variety of uses and categories, this column focuses on current practices and future trends in simulation research applicable to informing design decisions as part of building project delivery. Wherever possible, the authors have simplified the often complicated and competing terminology used in simulation research to provide the industry with a user-friendly typology of simulations. First, the authors present an overview of various simulation options and how they fit into the larger design and research framework. Second, they provide case studies from their experiences with simulations during project delivery. These case studies illustrate the various types of simulations and how they affect built designs. Finally, the authors summarize with commentary how simulations can be successfully incorporated in project delivery to optimize building design.Mock-Up and Simulation TypesTypes of mock-ups and simulation models used in design decision making include physical and virtual mock-ups, which are experiential in nature, and discrete-event simulation (DES) models and static models, which are computerbased methods to examine underlying systems within a building. (See Figure 1). Each of these mock-up and simulation models is explored in greater detail.Note: Within the listed computer-based simulations (CBSs), there is also the option to allow variability along a probability curve.Experiential Simulation ModelsExperiential simulation models (ESMs) allow hospital staff, clinicians, researchers, and designers to test care scenarios, including critical events such as an emergency code. They may have the greatest potential impact when the design of a particular area will be replicated frequently throughout a facility (e.g., a patient room, an exam room), or when a design has significant financial or health consequences (e.g., an operating or imaging area). Additionally, ESMs are used when there is interest in testing design innovations or a desire to improve existing practice (Watkins, Myers, & Villasante, 2008). …