Report Released: Energy Recovery Ventilation in MN Commercial and Institutional Buildings

May 1, 2017

CEE has released a final report on its research characterizing and improving energy recovery ventilation systems in Minnesota: Energy Recovery in Minnesota Commercial and Institutional Buildings: Expectations and Performance

ERV-diagram.jpgEnergy recovery ventilation (ERV) systems exchange heat and/or moisture between the outgoing exhaust air and the incoming outdoor (ventilation) air. These air-to-air ERVs are incorporated into mechanical ventilation systems and have the ability to reduce the resulting heating and cooling loads. 

Over the last 20 years, air-to-air exhaust energy recovery systems have become more common in Minnesota commercial and institutional buildings because of their potential for cost-effective energy efficiency benefits. While ERVs are in fact capable of achieving impressive savings of up to 80% of the ventilation air heating load, steps must be taken to ensure that units are installed and operated according to specification to reach performance expectations. Performance expectations should consider that practical implementation choices and performance under mild conditions will diminish savings with respect to design figures. 

The specific objectives of this study were to:

  • Characterize ERVs in Minnesota commercial and institutional buildings
  • Study a representative sample ERVs in detail
  • Characterize and improve ERV performance

Main Research Conclusions

This report found that a general lack of understanding around ERV performance has led to bad experiences with ERVs and their associated systems, creating negative perceptions and diminished expectations. However, these experiences and perceptions generally have little to do with the energy efficiency performance,todo more with the typical processes involved with implementing the technology. 

Mistakes relating to part failures, operator overrides, and installation account for 75% of the lost energy recovery. These mistakes persist due to unfamiliarity among operations staff and controls technicians as well as the absence of system feedback from poorly functioning ERVs. Fortunately, these mistakes can be easily corrected by commissioning new units to ensure that they function properly from the start. Problems with existing ERV systems can be easily identified by staff that are trained to understand ERVs and assess their operation. 

This project was supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program. The project was co-funded by CEE in support of its nonprofit mission to advance research, knowledge dissemination, and program design in the field of energy efficiency.

Related Links
Full Report: Energy Recovery in Minnesota Commercial and Institutional Buildings: Expectations and Performance
Webinar recording of project findings
Research project page