The HVAC industry has undergone a tremendous amount of change over the past quarter century — perhaps more so than any other sector of the building design industry. These changes have come about predominantly to improve the indoor environment, address environmental issues associated with refrigerants, reduce emissions, improve equipment efficiencies, reduce operating costs, and reduce life cycle costs. Some of these changes, such as the change in refrigerants, had little or no impact ion the complexity of HVAC system designs, owner involvement, or even the amount of design expertise required. The manufacturers had the bulk of the effort to change refrigerants, which required them to make the necessary changes to the equipment — coils, compressors, fan speed, etc. — and then provide the required performance data for the engineers, so they could fully understand the impact of those refrigerant changes. Similarly, changes required to increase equipment efficiency were, again, primarily the responsibility of the manufacturers and required very little increased effort on the part of the engineer other than to understand exactly what these changes were.
Many other changes had a much larger impact on the role of the design engineer. These changes were numerous and extensive, requiring the engineer to have a much deeper understanding of the products, their capabilities, and their installation and maintenance requirements. Some had additional spatial requirements — floor space, ceiling plenum space, or space on grade or roof. Many of these systems were more complex than systems previously designed and required more owner involvement during the design phase and, perhaps equally as important, required more knowledgeable owners and maintenance teams to properly operate and maintain these systems. There were many new systems that gained popularity for some of the reasons mentioned — improved air quality, higher efficiencies, etc. A partial list of these included such equipment and systems as air cleaning (filtration, UV, etc.), energy recovery systems (wheels, coils, etc.), geothermal systems, variable refrigerant equipment, solar and wind utilization, condensing boilers, improved airflow measurement, and many others.