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PREFACE:

The design engineer is responsible for considering various systems and equipment and recommending one or more system options that will meet the project goals and perform per the design intent.

 It is imperative that the design engineer and owner collaborate to identify and prioritize criteria associated with the design goals. In addition, if the project includes preconstruction services, the designer, owner, and operator should consult with a builder to take advantage of a constructability analysis as well as the consideration of valueengineered options. Occupant comfort (as defined by ASHRAE Standard55), process heating, space heating, cooling, and ventilation criteria mustbe considered when selecting the optimum system(s), as well as the following: • Temperature • Humidity • Air motion • Air/water velocity • Water quality and/or reuse • Outdoor air quality or purity • Indoor air purity or quality • Air changes per hour 

• Acoustics and vibration

 • Local climate 

• Mold and mildew prevention

 • Capacities (existing, proposed, and future expansion) 

• Redundancy

 • Spatial requirements (present and future) 

• Environmental health and safety design

 • Security

 •First cost

 • Return-on-investment cost

 • Energy consumption costs 

• Operator labor costs

 • Maintenance costs

 • Serviceability

 • Reliability 

• Flexibility

 • Controllability 

• Replaceability 

• Life-cycle analysis 

• Sustainability of design

 • Seismic protection

 • Filtration and filtration effects

 • Changing codes and standards 

Because these factors are interrelated, the owner, design engineer, operator, and builder must consider how these criteria affect each other. The relative importance of factors such as these varies with different owners, and can often change from one project to another for the same owner.

 For example,typical owner concerns include first cost compared to operating cost, extent and frequency of maintenance and whether that maintenance requires entering the occupied space, expected frequency of system failure, effect of failure, and time required to correct the failure. Each concern has a different priority, depending on the owner’s goals.