A Case Study: High Pressure Fogging for Vivarium Humidification/Evaporative Cooling and Lab Exhaust Cooling for Enhanced Energy Recovery

Mark Labac, Edge Mechanical Systems, Inc.
Joe Kimitch, University of Colorado Denver | Anschutz Medical Campus

High pressure fogging for vivariums and laboratories offers great energy savings over isothermal (steam) type humidifiers or evaporative pad based systems. This presentation addresses how to apply high pressure fogging technology, the psychrometric operation of high pressure fogging, actual system performance of a local installation and lessons learned on projects.

Vivariums typically need around 40-50%RH to be maintained in the space, thus humidification is typically required all year in arid climates. Using high pressure fogging in the supply air handling units offer a dual-purpose system. As the fog is injected into the airstream, the warm air absorbs the moisture thus providing the humidity required for the space. Even in the winter when the air must be pre-heated prior to the fog section, the energy use is still much lower than a steam based system. Since the fog is an adiabatic process, it cools the air and provides free cooling in the summer. Therefore, the system can be controlled based on both humidification and direct evaporative cooling.

In laboratory exhaust air systems, fogging is a method to increase the energy recovery system summer thermal effectiveness. Typical entering air temperatures for an exhaust energy recovery coil is around 75 F in the summer. In arid type climates, the fog can drop the entering coil temperature from 58 F all the way down to 46 F. These temperatures can be achieved in arid type climates as long as moisture is not added to the supply air of the laboratories. The cooling of the fog is directly related to the delta between the wet bulb temperature and the dry bulb temperature of the exhaust air stream. When fogging in the exhaust, the air stream can be fully saturated, cooling all the way down to the wet bulb temperature. Additionally, droplet filters are eliminated allowing the coils to get wet. This increases evaporation and reduces any added air pressure drop such as what you would get with typical evaporative pad type systems.

The University of Colorado at Anschutz has high pressure fogging systems on both the Vivarium supply units and Laboratory exhaust energy recovery units. In 2018, the high pressure fogging system saved over $83,200 in chilled water cost due to the evaporative cooling effect of the fog system. This energy savings cost includes the deduct of the water used for the fogging system. Results for the lab exhaust energy recovery system will be presented at the conference after it is trended the summer of 2019.

Lessons learned will be shared for the audience from multiple projects around the State of Colorado. The main items that will be addressed are water quality, maintenance, and AHU/ERU construction.

Learning Objectives

  • Describe how to apply high pressure fogging technology in both supply and exhaust units;
  • Explain the psychrometric operation of high pressure fogging in both supply and exhaust airstreams;
  • Analyze the actual system performance results running at University of Colorado Anschutz Medical Campus - Research Complex 1 in Aurora, Colorado; and
  • Investigate lessons learned on water quality and AHU/ERU construction considerations for high pressure fogging.


Mark Labac is President of Edge Mechanical Systems, a specialty Manufacturer's Rep in Colorado. The firm specializes in energy efficient equipment such as Accutrol, Composite Air Designs, Ingenia, MeeFog, and MK Plastics, with a strong focus on laboratory projects. Mark has a Bachelor of Science in Mechanical Engineering from Texas Tech University, a Professional Engineer License from Texas, and a LEED AP Accreditation. Mark is an active member of ASHE, APPA, ASHRAE, CAHED, I2SL, ISPE, & USGBC.

Joe Kimitch has 19 years' experience in the Building Automation System industry and manages the HVAC controls and network lighting systems on campus. He is the engineering department representative for design, construction, and commissioning of new buildings and retrofit projects. He assists in the program plan of deferred maintenance, controlled maintenance and energy conservation projects. Joe is an active member of APPA, IFMA, USGBC, and a Board Member of the Colorado I2SL Chapter.


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