Energy efficient design and indoor air quality are the two top challenges facing mechanical engineers today. Energy is rejected and wasted from all building in many forms. To minimize that loss, building envelopes have been made tighter and more energy efficient allowing us to reduce the cost associated with cooling or heating a building. In tightening the building envelopes, we’ve reduced the amount of outside air entering it. Yet, we need that outside air to remove the air contaminants generated indoors. Increasing the amount of outside air to flush these pollutants from the indoors to the outdoors has been the most effective way of reducing the indoor air contaminants to acceptable levels. This is the basis of the industry consensus and formalized in ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality.

What does all this mean for an “average” building? First and foremost, it will have some form of mechanical ventilation to provide controlled amounts of outside air to the building. To balance the building supply, an approximately equal amount of air has to be exhausted from the building. The result, wasted energy for the sake of indoor air quality. Imagine, a building owner/operator sitting next to the exhaust air discharge and throwing dollar bills into the air stream. The exhaust air stream represents a revenue stream wasted. The building owner/operator paid for this air to be cooled or heated. Not only did he pay for the air that is being exhausted, but he pays a second time for the ventilation air to be conditioned as well.

Can this waste be stopped? Yes, it can. And that is exactly what total energy recovery will do. The heating or cooling energy contained in the exhaust air stream can be recovered and used to precondition the outdoor air being brought into the building.