Energy savings for HVAC systems in health care facilities

Energy efficiency insights

• Energy-efficient strategies like variable refrigerant flow, active chilled beams and smart controls can significantly reduce energy consumption in health care facilities.
• Designing HVAC systems tailored to specific spaces within health care facilities is crucial for optimizing energy use and achieving compliance with stringent industry standards.

Health care facilities are among the most complex and demanding environments for heating, ventilation and air conditioning (HVAC) design. They require high levels of indoor air quality, thermal comfort, infection control and reliability while facing challenges such as limited space, stringent regulations and rising energy costs. To achieve optimal performance and sustainability, health care HVAC designers must apply energy-efficient strategies that balance patient, staff, visitor and equipment needs.

Figure 1: Mechanical room rendering designed to provide optimal performance and sustainability. Courtesy: Fitzemeyer & Tocci Associates, Inc.

Codes and standards for health care HVAC design

HVAC designs must follow the requirements established by various entities, such as ASHRAE, NFPA, the Facility Guidelines Institute (FGI) and the Centers for Disease Control and Prevention. Some relevant codes and standards for industry-standard health care HVAC design are highlighted in Figure 2.

Adherence to state and municipal codes is also necessary and, in many cases, such documents reference the above guidelines in their requirements. Meeting guidelines, such as FGI or ASHRAE, is also often a prerequisite for other health care business operations, including insurance coverage or public health department certification.

Figure 2: Table outlining the relevant codes and standards for industry-standard health care HVAC design. Courtesy: Fitzemeyer & Tocci Associates, Inc.

Health care as a building use is among the more regulated segments of design and construction. This often hinders the ability to design a more energy-efficient system through common solutions like reductions in capacity, diversities or setbacks. These guidelines tend to focus on exhaust increases and associated makeup airflows, filtration performance and air change rates, as well as tighter humidification ranges, which inherently add to energy usage.

Reasons for energy-efficient design and operation

Energy efficiency is likely to come with an additional first cost to cover things like more advanced technology or additional controls development. If designing for energy efficiency is made that much more difficult when navigating complex rules and guidelines, why would it remain a project goal? Several motivations should be considered.

Health care facilities consume a large amount of energy, especially within their HVAC systems, which account for about 45-55% of the total energy use in hospitals and 50-60% in outpatient facilities. By implementing energy-efficient measures, health care facilities can lower their utility bills, improve their financial performance and allocate more resources to patient care and quality improvement. According to a study by the American Society for Healthcare Engineering, a 10% reduction in energy use can boost the net operating income of a typical hospital by 1.5%.

More and more federal, state and local regulations and standards that aim to promote energy conservation are appearing. These serve to establish minimum standards and also offer assistance to achieve them. There might also be an incentive to improve on the minimum. In either case, the positive business case is likely inherent and there’s a business benefit to compliance. Additionally, for equipment that’s expected to be in service for a generation, there’s a benefit to future-proofing the facilities for standards we expect to continually develop.

Figure 3: MEP rendering of surgical suite, which requires high levels of filtration and low dewpoints. Courtesy: Fitzemeyer & Tocci Associates, Inc.

In New England, Mass Save, EnergizeCT and Efficiency Vermont are all state-backed programs that offer financial and technical assistance for energy efficiency projects that may be relevant to various health care applications. Federally, IRS Section 179D provides for available tax deductions on energy efficiency improvements, and further, the recent Inflation Reduction Act allows for nonprofits, including health care systems, to collect incentives or tax credits.

Energy-efficient HVAC systems help health care facilities reduce their greenhouse gas emissions and environmental footprint, which can contribute to mitigating climate change and its adverse effects on public health. Such alignment with the mission is a clear message to patients regarding the integrity of the facility. Lowering costs while also maintaining high levels of indoor environmental quality for patients, staff and visitors will increase patient satisfaction and care.

Health care facilities serve a unique role not only as businesses but also as civic institutions. The design can offer some opportunities from that perspective. Energy-efficient HVAC systems can demonstrate the commitment of health care facilities to environmental stewardship and social responsibility, which can foster a positive organizational culture and attract and retain talented staff.

Pursuing energy-efficient design and operations strategies in the health care sector is an important component in improving the economic, environmental and social performance of health care facilities. In a competitive market, it’s imperative not to dismiss energy-efficient solutions based on first cost. Instead, focus on the potential benefits to the health and well-being of their patients, staff and communities.

Integrating energy-efficient HVAC systems

There are numerous health care HVAC applications, from inpatient hospitals to outpatient specialists to residential care. Each project must always be evaluated on its own merits. There isn’t just one design strategy that’s always going to be the best, most energy-efficient choice. However, it’s important to remember the throughlines of ventilation and exhaust, air changes and filtration, which are the consistent drivers for health care HVAC. There’s no avoiding these potential energy hogs, but there are ways to reduce their impact.

An important concept that should be considered in almost any design is that systems should be designed for the space they serve and, conversely, systems shouldn’t serve spaces they aren’t designed for. On the surface, this seems obvious. The implication is that a system shouldn’t be under designed for its space. It goes both ways though. It can be incredibly wasteful to run an entire medical office building, for instance, through a unit designed to accommodate a space with the most stringent requirements.

Spaces where this is particularly important include operating suites, compounding pharmacies and other areas where high levels of filtration and low dewpoints are required. Consider how the design can reduce the amount of airflow required through a HEPA filter, across an eight-row chilled water coil or the mass of air that needs to be cooled to 48-49 F only to be re-heated back to a tolerable level. In terms of maintaining this type of unit, cleanliness is costly, both operationally and with respect to the first cost of a stainless-steel equipment upgrade to be kept sanitary more effectively.

Figure 4: Air handling unit (AHU) fans, which are an essential component of an HVAC system that help maintain temperature and humidity levels, and distribute air properly throughout a building. Courtesy: Fitzemeyer & Tocci Associates, Inc.

This is also applicable to a space like an emergency department that has heavy exhaust requirements. Energy recovery is most attractive at 100% outside air, and effectiveness drops as more mixed air is introduced. Running additional air across an enthalpy wheel doesn’t provide worthwhile benefit. It makes sense to provide the energy recovery ventilator (ERV) only for the emergency department, where it’s needed, and address adjacent spaces with a lower feature unit and economizer.

On the other hand, non-clinical administrative and office spaces can be divorced from any clinical system. There is often an opportunity to provide a small, flexible, self-contained system, such as a variable refrigerant with energy recovery that uses basic filtration and lower air change and ventilation rates to reduce the equipment load.

Energy savings with controls

One of the most straightforward ways to realize energy savings in any application is through controls, which can be retrofitted to an existing building management system (BMS). Smart sensors and controls can optimize the operation and performance of the HVAC system by reducing the energy waste. Through a fully integrated BMS, controls should also be set up to monitor as many key indicators as possible and adjust as needed. Not only should the building be looking to lower airflow and initiate setbacks based on timing and occupancy, but also at outdoor temperatures for hydronic temperature reset, solar conditions for automatic shades and historical trending to identify energy waste from a broken valve or actuator.

Finally, it’s important to remember that the controls design intent shouldn’t be neglected during operation. Resets and overrides are the enemy. To ensure they are operating as designed consider periodic re-commissioning and retro-commissioning, especially if the system has been in operation for 10 years or longer. As time goes by and operations “fixes” this, replaces that and adjusts the other thing, all without documentation, the properly designed system gets lost. Personnel changes in facilities departments can be a huge driver of inefficiency for this reason.

Variable air volume

The basic standard for health care design is a system of variable air volume (VAV) terminals with re-heat connected to a heating and cooling air handling unit with economizer ventilation. This system provides a straightforward way to accurately deliver a lot of air at a robust minimum outside air percentage to a lot of spaces. It also provides a means to control high humidity through sub-cooling and re-heat. If the AHU contains a humidifier, then low-limit control is also available. With all this in place, the basic needs of a standard health care design are met. While there are other design concepts that have been used extensively, such as constant volume and fan-coils, VAV is the most common default.

All VAV systems should be designed with appropriate setbacks. When not in use, conference rooms and shared spaces should be subject to CO2 occupancy sensing. Guidelines are inconsistent, but 1000 parts per million (ppm) is a reasonable maximum and it can be assumed that ventilation is not needed in that space at 200-400 ppm. Spaces that aren’t used 24 hours should be on a time scheduled setback, and overrides should have a timer on them as well. Consider using fan-powered terminals to facilitate actual unit shutdown overnight. Setbacks setpoints should be specified for airflow and for temperature.

Spaces that require pressurization monitoring typically provide an opportunity for setback management as well. For instance, a compounding pharmacy likely has a negative buffer room, positive buffer room and ante room, depending on the specific program. Consider including both supply and return VAV terminals in the design, so that the system can respond to both pressurization and minimum air changes. A dedicated pharmacy suite air handling system is important to realize this efficiency.

Terminal cooling

Another legacy concept is that of terminal cooling, often exemplified by zoned fan-coils. This type of system intends to reduce the amount of air that the system has to move in large quantities throughout the building, thereby gaining some energy savings. Drawbacks of these types of systems are often due to the inability to maintain tight conditions ranges, along with the maintenance of additional fans, motors or coils.  Specific to health care, these systems often are unable to provide the filtration requirements.

Figure 5: Part plan – project design documents. Note the relatively small size of the ventilation ductwork. Fan power and ventilation air conditioning are major energy uses in health care HVAC. Courtesy: Fitzemeyer & Tocci Associates, Inc.

Active chilled beams are an energy-saving terminal cooling technology that can reduce the fan power and cooling load of the system. These systems can apply to health care HVAC design under certain circumstances. An active chilled beam is a device that consists of a coil and air nozzle array. Room air passes through the coil and provides sensible cooling or heating to the space. The primary air supplied by the nozzle array is typically conditioned by a dedicated outdoor air system (DOAS), ERV or desiccant system that provides the required ventilation and humidity control.

Active chilled beams can be used in health care facilities that have medium to high sensible heat ratios, such as patient rooms, offices or corridors. This kind of system reduces fan energy by lowering the required primary airflow rate when compared to a VAV system, and eliminates the zone fans through the use of a high-pressure differential induction system. It also operates with a higher chilled water temperature (to stay above space dewpoint), reducing chiller energy consumption.

For specific project needs, active chilled beams can be a good option that could yield 30% energy savings over all-air systems and 20% over VRF. They have excellent temperature distribution and very low noise levels, but they are more costly to install and require a sophisticated hydronic temperature control system. This system is worth an evaluation where recirculation is allowed by ASHRAE Standard 170: Ventilation of Health Care Facilities.

Energy savings with VRF

Terminal cooling may be a legacy concept, but a relatively new and certainly still evolving, technology is VRF with dedicated ERV. VRF is a type of heat pump that can modulate the refrigerant flow according to the cooling or heating demand of each zone, thus reducing the energy consumption and improving the comfort level. VRF systems have become fairly common in recent years and are becoming more well known to building owners and users.

However, it may be that the biggest energy saving benefit is too often being value-engineered out or ignored altogether. VRF can be specified to be capable of simultaneous heating and cooling, meaning that, for instance, the heat rejected from the solar gain on the southern exposure on a cool, sunny day can be used to heat the spaces on the northern exposure. This is a massive benefit as any heat reuse directly reduces the energy requirement of the outdoor condensing unit and heat pump. Health care facilities often have diverse and dynamic thermal loads. Even with its high-cost, simultaneous VRF design should be evaluated in these cases.

It should be noted that VRF, like any terminal system, includes more equipment spread throughout the building, creating more opportunities for failure. If initial installation is not of a high quality, piping leaks will sap performance and efficiency. If maintenance is not upkept properly, system wear will also sap performance and efficiency.

Terminal cooling systems all share one major energy efficiency: each utilizes some form of energy recovery in its ventilation system when they get to be a certain size. This has been standard practice for years, as it is generally inexpensive to install and maintain. More recently, it’s been mandated by most relevant codes and guidelines.

While not always ideal for the central system of an inpatient hospital, terminal cooling offers many benefits for a satellite system or for an outpatient application.

Complexity of health care HVAC design

Health care HVAC design is a complex and challenging task that requires compliance with various codes and standards, often at the expense of energy efficiency. By providing the amount of ventilation air, filtration and cleanliness levels and the specific temperature and humidity conditions required, design engineers are continually introducing loads to the system. By utilizing some of the recommendations and practices outlined in this document, health care facilities can achieve HVAC systems that provide safe, comfortable and healthy indoor environments, while reducing energy consumption and costs.

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