Cooling System Selection

Selecting a building's comfort system represents a complex tradeoff between a number of different perspectives. Architects, engineers, contractors, building owners and developers have many things to consider. There are issues of first cost and operating costs. What does it take to operate a system? How is the space to be arranged and used? While the HVAC system may represent only 10 to 15 percent of the building's total cost, poor decisions in system design made today can result in significant problems for building occupants and owners tomorrow. There are the horror stories of sky high energy bills and almost everyone has heard about the sick building syndrome – buildings that suffer from inadequate ventilation or poor air distribution. There are other consequences of poorly designed HVAC systems. Poorly designed systems in retail space can affect product sales. HVAC design errors in a manufacturing plant can affect quality and productivity levels, and in hospitals and high tech operations, even the placement of the equipment can be critical.

As an illustration, consider an employee making $30,000 per year, occupying 150 square feet of conditioned space. The cost of that one individual can be expressed as $200 per square foot per year. This illustrates why occupant comfort is critical to a company's success. Even a 5 percent improvement in that employee's productivity can justify a replacement of the HVAC system. And the payback can be less than 2 years. That makes building owners sit up and take notice. But it's not uncommon for building owners to run low on money during construction. Budgets almost always end up being too small to include everything the building owner desires.

Therefore it's natural to see cuts made as the building nears completion. Unfortunately some of these well intentioned decisions to reduce HVAC installed costs come back to haunt the building owner and occupants in the future. The key to success in the partnership between the designer and the building owner/developer is to look at the building's overall HVAC system from a first-cost and an operating-cost perspective. The owner may also be influenced by a system's flexibility in adapting to changing occupants and changing use. This evaluation requires the understanding of at least five different variables. Comparative equipment cost and energy performance, energy prices today and projections for the future, operation and maintenance costs, operating characteristics of the system and past experience with HVAC systems.

The situation is even more complicated today with the phase out of certain refrigerants, tighter regulations, and heightened concerns over air emission and global warming gasses. There are a wide range of design options, trade-offs and considerations.