Description:

Airside economizers are used to increase the amount of outside air drawn into a building when outside conditions are cool and the system requires cooling. They reduce the amount of energy required for mechanical cooling.

For most commercial buildings, outdoor climate and indoor climate needs are the main factors in determining whether or not to use an airside economizer cycle, and which type of control to use. Ongoing maintenance costs can also be a factor in choosing which type of control to use.

In the hot and humid climate zone, economizer cycles are typically not used since outside conditions are not cool enough for enough hours to make their use cost-effective. For other climates, many economizer control options exist, including single point dry bulb temperature (OA), differential dry bulb temperature (OA & RA), single point enthalpy (OA), and differential enthalpy (OA & RA). This measure consists of upgrading the economizer controls for more energy efficient operation and reduced maintenance costs.

While enthalpy-based economizer control may be more energy efficient than temperature-based control in some climates, especially humid climates, enthalpy sensors are often inaccurate due to the typical high level of error related to relative humidity sensors, even in new sensors. It is often more cost-effective to use temperature-based economizer control when sensor error and maintenance costs are factored in.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.