Here are some tips and tricks for designing HVAC systems in health care and hospital buildings.
HVAC insights
- A recent HVAC project at a cancer center demonstrated how integrating heat pump systems into a health care facility can balance stringent environmental controls with long-term energy goals.
- The design team used heat recovery chillers to ensure the health care facility could reclaim rejected heat for critical functions while maintaining reliable performance during wide temperature swings.
- The result was a health care facility that strengthened both clinical operations and overall energy efficiency in the HVAC system.
Describe a project in which you have specified heat pumps. What was the challenge and its eventual solution?
Brad Reuther: Central heat pump chiller-heaters are becoming more common when implementing electrified buildings. A challenge with air-source heater-chillers is that heating output capacity varies based on the availability of a simultaneous chilled water load as well as outdoor air temperatures and defrost cycles. On a current project the primary focus has been to maximize the year-round chilled water load available for heat recovery to minimize potential heating capacity variations. Waste heat sources such as mechanical/electrical rooms, data closets, foodservice walk-in coolers/freezers and MRI cooling are all cooled locally with chilled water. Many other spaces throughout the building utilize active chilled beams. Boilers provide additional heating capacity for short duration peak heating conditions.
Meagan Gibbs: At a cancer center in Omaha, we integrated heat pump technology into a highly complex research and patient-care facility. The challenge was designing a system capable of maintaining precise temperature and humidity for sensitive cancer treatment spaces — including bone marrow transplant units — while still meeting the client’s long-term carbon reduction and energy efficiency goals.
Our solution was a heat recovery chiller/heat pump system tied into the central plant. This allowed the building to reclaim heat rejected during cooling and reuse it for reheat and domestic hot water generation, rather than relying on steam boilers. The system was designed to perform reliably during the region’s wide temperature swings, ensuring uninterrupted operation for critical care areas.
The result was a facility that not only provides state-of-the-art cancer care and research, yet also demonstrates how advanced heat pump integration can lower energy intensity in one of the most demanding health care environments.
Darren Harvey: Water cooled heat pump chillers are becoming common in central energy plants to meet the requires of IECC or ASHRAE 90.1…especially when airside economizer isn’t feasible or a good choice based on ambient conditions. A challenge with heat pumps is sizing and installing them correctly to be effective in all operating conditions. Additionally, waste heat from the heat pump chillers must always have a source to be dissipated or connected to the condenser water loop, which often isn’t operationally cost effective.
What unique heating or cooling systems have you specified into such projects? Describe a difficult climate in which you designed an HVAC system for a hospital, health care facility or medical campus project.
Brad Reuther: A current project in Arizona is in a location prone to wildfires and dust due to the dry climate. In addition, several air handling units are in relatively close proximity to a helipad serving the building. Electronic air filters and Bipolar ionization both offer solutions to minimize the amount of these pollutants brought in through the outside air. Carbon filters offer an additional level of protection for difficult to remove helicopter exhaust fume odors. AHU controls include an air quality mode that switches AHUs into minimum outside air mode. On site air quality monitoring sensors as well as web-based information sources alert facility engineers when Air quality mode may be needed.
Meagan Gibbs: In Omaha, we designed a new Central Utility Plant to support the 425,000 sq. ft. expansion of a local hospital . The chilled water system was designed to initially serve the expansion with capacity to support approximately 300,000 sq. ft. of existing campus buildings as well.
One of the most complex aspects of the design involved the condenser water system. The system needed to support both the newly constructed chiller plant and the 25-year-old chiller plant. This was a necessity as the existing cooling towers were located in the footprint of the expansion.
The new condenser water system was designed with a 10-degree delta T, while the existing chilled water system operated at a 14-degree delta T. The design team reconfigured flow rates for the existing chillers to accommodate the higher flow and reduced temperature differential, ensuring compatibility and performance.
The existing condenser water piping was intentionally sized to allow future conversion to chilled water piping, enabling long-term flexibility and minimizing infrastructure disruption when the current chiller plant is eventually decommissioned.
How have new outside air requirements affected energy efficiency?
Jason Butler: The pandemic certainly resulted in an increased focus on both outdoor air and filtration. Increasing both of these has directly associated energy penalties. Some solutions have included adjustable outdoor air intake (i.e. only employing once-through air system mode when deemed necessary) and energy recovery on exhaust airstreams.
How have code changes and specifically the switch to A2L refrigerants, impacted the design of new and existing health care facilities?
Caleb Marvin: Patient safety remains the first priority in health care design where A2L refrigerants present an additional layer of design considerations. The designer must understand the volume of each space and the ventilation requirements if the charge of refrigerant leaks. With fully ducted HVAC systems and most walls extending to deck, space volume is limited. Where DX systems are used in a health care facility, A2L refrigerants present an additional challenge requiring special care in system selection and design, sequence of operation and ventilation.
Brad Reuther: The refrigerant transition has impacted health care facilities similar to other building types, however health care facilities such as hospitals and nursing homes fall into the institutional category which cuts in half the allowable refrigerant quantities calculated per ASHRAE 15. A2L use is primarily limited to high pressure systems using scroll compressors. When evaluating indoor equipment types such as chillers, the additional requirements associated with A2L refrigerants may drive system selections toward low or medium pressure refrigerant types including screw or centrifugal compressors using A1 refrigerants. Unitary and split DX systems that are transitioning to A2L refrigerants also should be evaluated against water based cooling systems depending on size and mitigation requirements.
Meagan Gibbs: The transition to A2L refrigerants is one of the most significant HVAC code-driven shifts we have seen in recent years. For health care facilities, this introduces both design challenges and opportunities. Unlike commercial office or residential projects, hospitals require continuous operations, stringent infection-control measures and life safety protections that complicate refrigerant selection and system layout.
With A2Ls’ lower global warming potential, the switch supports long-term decarbonization and ESG goals, however their mildly flammable classification means mechanical rooms, piping distribution and detection/ventilation strategies must be carefully rethought. We have been incorporating enhanced leak detection, ventilation interlocks and zone isolation strategies into our recent designs to maintain NFPA and ASHRAE 15/34 compliance without disrupting patient care.
On our extra-large medical campus projects, the scale of chilled-water and refrigerant distribution systems demand new approaches. For instance, where possible we have paired centralized chilled-water plants with localized A2L-based VRF systems in non-clinical zones, balancing safety with energy performance.
Ultimately, A2L adoption is accelerating innovation in health care HVAC. It is driving integration of digital monitoring, early-warning systems and smarter zoning that not only address refrigerant safety yet also enhance overall resiliency of building systems.”
Jason Butler: The changes in refrigerant requirements have been a significant impact to the building industry, including health care facilities. The pace at which manufacturers have had to meet the changing regulations has created supply chain challenges and increased the amount of hiccups and troubleshooting done in the field during startup.
Darren Harvey: For many years, upgrades in refrigerants were a positive step in energy efficiency gains. While the newer refrigerants are safer and better for the environment, we’re seeing lower efficiency ratings for similarly sized equipment and those energy saving opportunities are having to be shifted to other equipment.
How have you worked with HVAC system or equipment design to increase a building’s energy efficiency?
Caleb Marvin: I have designed multiple boiler replacements to replace existing firetube boilers with condensing style hydronic boilers, improving the overall heating plant efficiency. Condensing boilers increase in efficiency with lower heating water return temperatures with efficiencies up to 95%, beating out standard firetube boilers with typical efficiencies around 80%. Heating water temperature reset sequences can help maintain a return water temperature as low as possible to maximize efficiency. The engineer’s analysis for these types of retrofits must account for the loads served and the ability to meet temperature and load requirements with lower temperature heating water. In addition, a small steam boiler or point of use steam systems for sterilization and humidification may be necessary.
Meagan Gibbs: For most hospitals, heat recovery chillers offer an effective solution for improving energy efficiency. Heat recovery chillers can simultaneously supply chilled water and heating hot water all year-round for a variety of hospitals needs – including heating, cooling, process cooling, pre-heat for domestic hot water and snow melt.
Jason Butler: One system type that has gained some traction in health care is the use of chilled beams. While not appropriate for some areas of hospitals, in standard patient rooms it can provide an energy saving alternative to traditional ‘all air’ systems.
What is the most challenging thing when designing HVAC systems in such buildings?
Caleb Marvin: The most challenging item when designing HVAC systems in health care facilities is balancing facility requests and optimal efficient design with project budgets. Many owners and facilities want to explore many energy-saving design elements and maximize the control of individual space conditions. As construction costs rise at an unprecedented rate, it is important to work with contractors along with the architect and owner to analyze options and make recommendations to the hospital that provide the right solution the project budget.
Meagan Gibbs: Budget is extremely challenging as it becomes difficult to reduce overall MEP budget without reducing the quality and resiliency of the systems.
Jason Butler: One key challenge in engineering design and a big way to help facility operations in the future, is designing for maintainable redundancy. Often, this means incorporating N+1 or 2N redundancy, but with an eye towards maintenance or replacement while maintaining the whole system in operation. Maintenance, repair and replacement on critical systems need to be able to be done without shutting systems down, since so many critical areas need to be operational 24/7 and can’t accommodate planned shutdowns like many non-health care applications can.
What systems are you putting in place to combat hospital acquired infections (HAI)?
Caleb Marvin: There are multiple ways to combat hospital acquired infections (HAI) in response to several specific illnesses that have risen in the past years. A pandemic mode where an exhaust system is tied into the return with motorized dampers to isolate a patient wing forcing the patient rooms negative has been implemented for future pandemic response. The outside air must be reset in this mode to maintain a slightly positive building requiring dehumidification/humidification of the additional outside air Many of our recent designs also have dedicated air handling units for the Emergency Departments, preventing the air from being circulated to other areas of the hospital.
Brad Reuther: ASHRAE 170 has many requirements geared towards reducing HAI’s. Key components include minimum requirements for ventilation rates, total air change rates, exhaust rates, space pressurization, filtration levels and temperature/humidity ranges. Additional HVAC system components commonly used or evaluated to further reduce risk include UVGI at cooling coils, bipolar ionization in the supply air stream, integrated ceiling systems in operating rooms. Local solutions include upper room UVGI and high efficiency filtration units. Plumbing systems are another focus area to reduce HAI risks through water treatment, limiting potential for stagnant water in piping and minimizing splashing at plumbing fixtures.
Meagan Gibbs: One of the systems we have been implementing to eliminate bacteria, virus, mold and volatile organic compounds in the air – improving overall indoor air quality – is needlepoint bipolar ionization. This generates cold plasma in the air replicating the same positive and negative ions found in nature. As these ions come into contact with airborne pathogens, they engage with surface proteins and render them inactive.
Jason Butler: The most direct impact we have have with the engineered systems are; air changes and filtration and laminar and effective airflow in operating rooms & other critical procedure spaces.
Darren Harvey: Strategies around HAI reduction are complex and require good infrastructure and diligence in operational practices from caregivers, maintenance personnel and in some cases, patients own family members. From an infrastructure standpoint, we have studied and implemented several hybrid airside filtration systems that use both electronic means and standard filter media and found a dramatic decrease in particle count reductions in operating rooms and procedure room settings. The newer electronic filtration systems work, but need to be installed and operated as they were intended. We’ve also seen hospitals and ambulatory facilities implement systems in ways they weren’t intended to be used with little to no improvement in air quality.
What type of specialty piping, plumbing or other systems have you specified recently? Describe the project.
Caleb Marvin: Water quality for sterilizing equipment in sterile processing departments challenges many facilities as they cannot choose the quality of the city water incoming. RO/DI systems help increase the longevity of equipment and prevent spotting on instruments and utensils. These systems are being implemented even more as health care providers look to implement ANSI AAMI ST108 in their facilities as best practice and with speculation that ST108 will soon be adopted by CMS. A recent project replaced existing sterilizers, washers and a cartwash in an older facility by expanding the entire sterile processing department. A water softener was added to remove minerals from the water as a first stage of the process, with softened water piped to some sterilization equipment not requiring high purity water. An RO/DI system then produced pure water, which was piped in a loop for the final rinse of the equipment.
Medical gases are vital for hospitals and medical campuses. Describe a project, its goals, the challenges and the design solutions that involved medical gases.
Caleb Marvin: Verifying and ensuring the bulk oxygen yard is adequate for campus expansions is crucial during a master planning process for hospital campuses. A project added a patient tower sized for 60 additional patient beds to a campus that was already taxed on the existing bulk oxygen system. A new bulk oxygen yard was coordinated in a separate location and a dedicated line was provided to the new tower. A separate new line backfed the existing feed to the original campus. This additional site work in an existing campus allowed the opportunity to use corrugated metal tubing that did not have to be trenched the entire way like standard piping. This limited the interruptions to the existing facility, including maintaining the ambulance drive, while providing a needed upgrade to their oxygen system.
Darren Harvey: Medical gases are code required in hospitals and centralized piped systems are common. Piped nitrous oxide systems are known to have a high leakage rate from the piped systems, fittings and regulating devices…studied to be 70-95% on average. On a recent replacement hospital, we studied the ability to eliminate the campus wide piped nitrous oxide system and instead provided bottled gas rooms closer to the point of use. While this approach required some operational changes for the hospital, there will be a major savings in nitrous oxide consumption. The approach also reduced the construction cost by eliminating long runs of copper medical gas piping.
