Enhancing energy efficiency for HVAC systems in health care facilities

HVAC insights:

• Air-cooled chillers and dedicated low-temperature chillers can optimize energy efficiency and maintain precise temperature control in healthcare facilities.
• Increased code requirements demand energy-efficient strategies, like heat recovery chillers, to balance HVAC loads while maintaining compliance.

Respondents: 

• Cory Duggin, PE, LEED AP BD+C, BEMP, Principal / Senior Energy Wizard, TLC Engineering Solutions, Brentwood, Tenn.
• Benjamin Medich, PE, Vice president, HDR, Pennington, N.J.
• Daniel Noto, PE, LEED AP, Southeast market leader, Fitzemeyer and Tocci Associates, Alpharetta, Ga.
• Kevin Jayne, PE, LEED AP, Principal. Affiliated Engineers, Inc., Denver, Colo.

What unique heating or cooling systems have you specified into such projects? Describe a difficult climate in which you designed a heating, ventilation and air conditioning (HVAC) system for a hospital, health care facility or medical campus project.

Kevin Jayne: A chilled water plant analysis for a local Denver community hospital identified air-cooled chillers as the optimal system design to balance initial costs with efficiency. These chillers minimize maintenance requirements, reduce water usage and simplify winterization. To meet the hospital’s demanding operating room temperature requirements, especially during Denver’s hot summers, we integrated dedicated low-temperature chillers. These chillers sufficiently suppress the supply air dewpoint by utilizing multiple chilled water coils that are piped in series to ensure a stable, controlled environment for surgical procedures.

How have new outside air requirements affected energy efficiency?

Kevin Jayne: Standards continue to advocate for increased air ventilation in healthcare settings to enhance occupant comfort and support improved infection control. However, these additional air ventilation requirements also raise HVAC building loads. To comply with energy code requirements, designers should employ progressive strategies such as heat recovery chillers to offset the added ventilation load by leveraging the simultaneous winter cooling and summer heating loads. A similar effect occurs with increasingly strict filtration requirements, which impose additional electrical loads due to the increased fan power needed to overcome elevated pressure drop.

Daniel Noto: As outside air requirements increase, the challenge to maintain energy efficiency becomes a more difficult task. Understanding and implementing other techniques, such as filtration options, allows for code compliance with the intent for higher indoor air quality without increasing outside air requirements to the point of decreased overall efficiency.

What unusual or infrequently specified products or systems did you use to meet challenging heating or cooling needs? This might include active chilled beams, variable refrigerant flow, etc.

Kevin Jayne: Active chilled beams decouple the ventilation load from room-level space conditioning. By supplying only the minimum required ventilation air to a chilled beam, space temperature control is managed through a chilled and hot water coil overhead at the room level. The coil remains dry by maintaining the chilled water supply temperature above the space dew point, allowing the chilled beam to naturally create a well-mixed environment. We’ve designed active chilled beams for patient room applications in Colorado, where the semi-arid climate provides an especially opportune application.

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

Daniel Noto: Balancing the desire to keep energy costs low while ensuring the overall design cost is within the owner’s budget is an ongoing challenge for any project where energy efficiency is important to the user.

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

Daniel Noto: More than anything else, proper room pressurization is key to mitigating the spread of HAI. Having room pressures constantly monitored and controlled through an automatic system that adjusts based on changing conditions such as doors being opened, filter loading, etc. is key to this mitigation.

Medical gases are vital for hospitals and medical campuses. Define the project, its goals, the challenges and the design solutions.

Kevin Jayne: The pandemic heightened awareness of medical gas-consuming equipment, such as ventilators, as existing infrastructure struggled to meet the heightened medical air and oxygen demands due to the surge in patients. Double-occupancy patient rooms further strained system capacities. To address this capacity constraint in a new inpatient tower, we increased the branch pipe sizing on patient room floors. We found that even a single nominal pipe size increase can significantly enhance capacity while incurring minimal additional costs. In some hospitals, oxygen consumption analysis during peak periods led to heightened pipeline supply pressure at the bulk farm, maximizing the existing system’s available capacity.

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