Exhaust air energy recovery provides many opportunities to reduce overall energy consumption by recycling low-grade waste energy, which would otherwise be exhausted to the atmosphere, to pre-treat outside air and reduce the heating, cooling, humidification and dehumidification requirements of the space. When used correctly, air-to-air energy recovery ventilation (AAERV) delivers on this promise and provides one of the most economical ways to create high performance, well ventilated indoor environments. However, when used incorrectly either through incorrect placement of the device or through a poor understanding of controls, anticipated savings may not be realized. One of the most obvious opportunities for savings with any air handling system is through the use of an airside economizer, which is why it is mandated in ASHRAE Standard 90.1. Airside economizers are generally well understood, but there are several details that are important to consider when employing an economizer together with air-to-air energy recovery. However, before selecting an effective strategy, we must first understand what is required in order to comply with ASHRAE Standard 90.1; we will look at Section 6.5.1.1 and 6.5.6.1 in addition to reviewing key excerpts from the ASHRAE 90.1 Users Guide. Armed with this information, we can examine the different types of AAERV technologies (sensible, total, active and passive) and see how an effective airside economizer may vary by device. We will also examine 100% OA, Dedicated Outdoor Air Systems (DOAS) in addition to applications that only require a minimum amount of outside air to ensure that the exchanger is in the correct location, that the economizer is correctly sized and that the proper control sequences are conceived and implemented with several practical examples. Finally, we will look at some of the regional requirements and variations across North America and determine where and when exhaust air energy recovery can be used most cost-effectively in conjunction with an effective airside economizer. The result will be a better, practical understanding of AAERV and airside economizers to ensure that maximum performance and savings can be realized.