Excessive use of safety factors in the design of a dedicated outdoor-air system (DOAS) can result in significant over-ventilation and larger-than-necessary equipment. However, design decisions are often based on incomplete information and assumptions that may or may not be valid, so safety factors are important tools for the design engineer. This paper discusses several of the common uses of safety factors in the design of a DOAS, and provides recommendations on how to design a system with "reserve capacity" to accommodate unexpected loads and the need for increased airflow or dehumidification capacity, while minimizing the impact on installed cost and energy use.

Units: Dual