COP is a dimensionless ratio of the power output of a unit to the electrical
power required to run it. EER can be converted to COP by dividing by 3.413
BTU/(W*hr).
Efficiency in HVAC systems has increased steadily over time due to advances in
technology and rising energy prices. Efficiency has also increased due in large part
to federal laws and national efficiency standards. The National Appliance Energy
Conservation Act (NAECA) and the Energy Policy Act (EPAct) have established
minimum-efficiency standards for furnaces, boilers, and packaged equipment to
which manufacturers must comply, and the standards are updated every few years.
The American Society of Heating, Refrigerating, and Air-conditioning
Engineers (ASHRAE) has created many of the standards that have eventually
been adopted as requirements, code and law. The ASHRAE/IESNA Standard
90.1 provides the basis for most HVAC efficiency requirements in the United
States. Compliance with the standard is a prerequisite for Leadership in
Energy and Environmental Design (LEED) certification for new construction
to demonstrate minimum energy performance of a building.
ASHRAE/IESNA Standard 90.1 includes efficiency requirements for equip-
ment not included in federal laws such as EPAct and has been adopted as the
commercial building energy code in many states. Because highest efficiency equip-
ment can sometimes reach a cost-effectiveness limit there are federal and utility-
sponsored programs that provide cash incentives for choosing such equipment.
Strategies for Maximizing HVAC Efficiency
Heating, ventilation, and air conditioning account for a substantial portion of
commercial building energy use and costs. In residential buildings, ventilation
can be provided by windows and structural air leaks even if ventilation is not being
provided by the HVAC system. Commercial buildings have mandatory ventila-
tion requirements so the HVAC system provides most of the ventilation for the
building at all times. Commercial buildings also have much higher thermal loads
due to lighting systems, electronic equipment, and a higher density of people,
and these loads grow larger as more floor space and levels are added to a building.
For all of these reasons increasing the efficiency of a building’s HVAC sys-
tem can result in dramatic savings over time. Numerous strategies have
emerged to increase the efficiency of HVAC systems.
Reducing Loads
A major step to maximize HVAC efficiency in a building is reducing heating
and cooling loads. Reducing heating loads is as simple as installing more
40 Smart Building Systems for Architects, Owners, and Builders