The engineering design of a complex building is usually divided into several disciplines: HVAC, electrical, plumbing, and fire protection. Each area is budgeted a certain amount in time as part of the project manager’s completion schedule. With very few exceptions, the HVAC design of a new project is the most time-consuming and labor-intensive. The HVAC systems consist of carefully balanced fans, coils, ductwork, and control devices. A modification in any HVAC component can have unforeseen circumstances on the performance of the whole system. For example, reducing the airflow by slowing the fan may save in power needed to operate the fan. However, the air may not be adequately cooled as it flows across the coils, the finned devices that transfer heat to or from the air. Also, the ductwork may not deliver the proper volume of air to each space, especially the zones most distant from the air handler. In either circumstance, you can save fan horsepower but still use more total energy to condition the air because the fan would have to run longer.
It’s essential, then, to consider the overall effect of changes made to any portion of the HVAC system. These analyses can be quite sophisticated, especially for a large building with dedicated chillers and boilers. Fortunately, there are many energy-conserving projects that can be done to optimize the overall operation without causing an imbalance in the other mechanical systems. These projects should be done before any work is done on the main components of the system— the chiller, boiler, or pumps. The energy-conservation measures in this section are arranged in order of increasing expense and complexity.
The more expensive projects should be justified on the basis of a system whose components have been optimized by the implementation of the projects previous in the hierarchy.
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Excerpt from Energy Conservation Projects.