The presentation will introduce development tools and design considerations used in HVAC controls development. Controls development use simulation, lab testing and field trial at different phases of the project cycle to improve control performance and to achieve rapid development. Development starts with simulation to originate and define algorithm concept. The concept is then implemented in a prototype controller, and tested in lab environment. The concept is refined and verified by analyzing lab results. In the final phase of development, controllers with refined and verified algorithms are installed in field trial sites to ensure system integration and to confirm customer perceptions. Examples are given to illustrate control-related focus areas in each of these three phases. Advantages and disadvantages of different tools are explored in the presentation. In addition to development tools, various analysis methods are used in all development phases to define controls requirements, to enhance existing algorithms, and to evaluate control performance. Examples of operating map analysis, algorithm techniques, and design trade-offs are used to demonstrate current development practice. Several algorithm improvement potentials are identified and discussed.