How are hospital HVAC systems being designed differently?

Respondents:

• Mark Chrisman, PE, PhD, Healthcare Practice Director, Principal, Henderson Engineers, Lenexa, Kansas 
• Mike Fialkowski, PE, RCDD, LEED AP, Technology Services Market Leader, Affiliated Engineers Inc, Madison, Wisconsin 
• Zach Frasier, PE, Mechanical Engineer, Moses Engineering, Gainesville, Florida 
• Steve Lutz, PE, LEED AP, Associate Director, Harris, St. Paul, Minnesota 

How have you and your team addressed the unique air requirements of COVID-19?  

Mark Chrisman: We have used a variety of approaches depending on the unique needs of a facility and the overall goals of a project. The most important aspect of this type of retrofit is understanding where to focus our resources. We have had projects with a lack of negative pressure rooms where a full renovation of the HVAC system was required to meet the needs of the facility. Other facilities have required us to simply focus on patient waiting areas because using air cleaning units in those spaces was a better value than undertaking full heating, ventilation and air conditioning upgrades. 

Zach Frasier: Airborne viral infections such as COVID-19 requires specific life safety, HVAC and patient flow design to ensure separation of positives from persons under investigation. 

What unusual or infrequently specified products or systems did you use to meet challenging heating or cooling needs?  

Zach Frasier: We’ve specified the largest magnetic bearing chillers that were, at the time, the largest in the world. As part of that project, pressurized heating hot water boilers producing 220°F were also specified.  

Steve Lutz: Heat recovery chillers seem to meet the needs well.  

How have you worked with HVAC system or equipment design to increase a building’s energy efficiency?  

Mark Chrisman: We have zoned air handling units to maximize the allowed supply air reset at the main AHU coil to reduce the reheat load and chilled water load at the central plant.  

Zach Frasier: Generally, energy efficiency projects in hospitals involve right-sizing the ventilation system. For example, many former radio medicine facilities use single pass air; these facilities have since located modalities that do not have these facility requirements. The engineering solution was to replace the HVAC system with a recirculating air system.

What is the most challenging thing when designing HVAC systems in such buildings? 

Mark Chrisman: The biggest challenge is balancing code required air change rates, humification and dehumidification requirements with reducing the HVAC system’s energy usage. 

Zach Frasier: The most challenging aspects of designing hospital HVAC systems is working within the existing physical limitations of the building while maintaining facility and modality uptime. 

Steve Lutz: Different building occupants can require very different thermal comfort conditions in very close proximity.  

What systems are you putting in place to combat hospital acquired infections? 

Mark Chrisman: We review many of the new air cleaning technologies that emerge to ensure we’re putting our best foot forward. The most important criteria for adopting a new system are whether there’s substantial evidence on how effective it is. However, implementing good room airflow patterns and room pressurization is still one of the most underrated ways to minimize HAI. Air cleaning technology can be a supplement to these design practices but should not be a substitute. 

Zach Frasier: System design implementation varies by the modality space use and the hospital’s identified HAI vectors. For example, we have specified copper coils and HEPA filtration for operating rooms where the staff use chemicals that decompose into hazardous materials when exposed to UV light. 

Steve Lutz: High levels of MERV filtration and ultraviolet systems are commonplace.  

What type of specialty piping, plumbing or other systems have you specified recently?  

Zach Frasier: We’ve specified all of the piping infrastructure in hospitals. For retrofit work, the primary challenge is coordinating hot work. As a result, most of this work uses mechanical couplings or interference fittings where accepted by the facility. 

Steve Lutz: Instead of traditional cast iron piping, epoxy coated cast iron piping was used. It offers longer life and avoids future disruptions and costly repairs. 

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