Energy Star tax credits
Simple is as simple does. It works. Its easier to understand. Easier to fix. The real world does not reward complexity.
An important aspect of good design is simplicity. HVAC can be complicated enough, given the need to maintain various spaces at set temperatures, relative humidity and cleanliness. HVAC systems are also expected to maintain certain pressurization and [code required] outside air exchange. All while keeping to the highest possible energy efficiency. We also need and expect them to respond precisely and correctly to changing variables.
Simplicity in controls are also key to this. The simplest controls are on-off. Simplicity is not obvious everywhere. But in reality, as software development theory teaches, you can find the simple by decomposing the complicated.
Consider these concepts before the initial Basis of Design is established. Decompose the various functions needed and decide how the system will be controlled. Many designers have their personal preferences and presumptions, but these must be put aside in favor of open-mindedness in the beginning of the decision making process. Yes, energy and size calculations may be useful, but not as important as what and how to control the various environmental parameters.
Diagrams of the systems, 
Continue reading Modularity and HVAC systems design
