Designing health care facilities and medical campuses: HVAC and plumbing
- Andrew Flanagan, PE, GPD, LEED AP, Associate, Senior Plumbing Engineer, Interface Engineering, Portland, Ore.
- Mikhail Fuks, PE, HFDP, Engineering Group Leader, P2S Inc., Long Beach, Calif.
- Gary Hamilton, PE, LEED AP, CxA, EDAC, SASHE, Senior Vice President, WSP, Arlington, Va.
- Alex Harwell, Client Manager/Project Manager, Dewberry, Raleigh, N.C.
- Ted Hood, Senior Project Manager, TLC Engineering for Architecture, Brentwood, Tenn.
- George P. Isherwood, PE, Vice President, Peter Basso Associates Inc., Troy, Mich.
- Jeremy Jones, PE, LEED AP, EDAC, Healthcare Market Leader, Affiliated Engineers Inc., Chapel Hill, N.C.
- Brian Kannady, PE, Principal, ME Engineers, Golden, Colo.
CSE: What unique heating and cooling systems have you specified into such projects? Describe a difficult climate in which you designed an HVAC system.
Hamilton: For the Allegheny Healthcare Network project that I am designing, we had a very hot climate. We designed a factory-built modular central plant that is external of the hospital. To meet the LEED Silver requirement, we had to use a heat pump chiller to improve the efficiency of the system. During this planning phase, the engineering team provided a control system that ensured the most effective and efficient system criteria for the hospital’s utilities. The heat pump was designed to operate in parallel or series and boosted overall system efficiency.
Jones: We have implemented active chilled beams into numerous health care settings including patient rooms, and we are fully comfortable in continuing to do so. The health care industry is historically conservative for all the right reasons, but that doesn’t mean there is no room for innovation. We collected pre- and post-occupancy data on the most significant of our active chilled-beam projects, which proved a reduction in energy usage, an increase in patient satisfaction (at least as it relates to hot and cold calls), and a reduction in infection rates. To be clear, we are not claiming that the installation of chilled beams is responsible for the reduction in infection rates, only that the data certainly does not support the notion that the recirculation inherent in active chilled-beam operation results in an infection risk, as some naysayers contend. This project is located in a humid part of the country, and in 4 years of occupancy, we have had no instances of condensation on the beams. This was achieved primarily through intentional monitoring of the patient-room conditions combined with the ability to reset secondary chilled-water temperature.
Harwell: Designing systems to achieve very narrow temperature and humidity-control bands in operating rooms in the Southeast United States. The current expectations of surgeons for very low temperature and humidity conditions are often well beyond the capabilities of their existing HVAC systems, especially standard house chilled-water temperatures. This has required the installation of additional dehumidification systems dedicated for HVACs serving operating rooms and other critical control areas.
Fuks: Tackling monsoon seasons in Arizona’s climate, in which it will rain but also be very hot and humid (100°F), has been challenging for air-handling equipment design. The air handling equipment must have substantially larger cooling coils to deal with a large amount of moisture removal prior to entering the building.
CSE: What unusual or infrequently specified products or systems did you use to meet challenging HVAC needs?
Fuks: The commercial and health care HVAC worlds have been colliding lately. We now regularly specify refrigerant-based systems (including variable refrigerant flow (VRF)) for health care projects due to limitations in central heating/cooling systems at remote site clinics, surgery centers, and outpatient facilities. This trend will continue to pick up speed as health care facilities move into retail and residential centers to expand the patient experience. Hamilton: The heat pump chiller and the modular central utility plant as mentioned before are examples.
CSE: Have you specified a radiant heating or cooling system into a hospital or health care building? Describe the project.
Hamilton: I have once used radiant-heating panels to provide perimeter heating to supplement a variable air volume (VAV) system with reheat, but they were not used as the main heat of a cooling distribution system. This was in place of finned-tube radiators. The architects hardly ever like to see fin-tube heaters at the bottom of their full-height glazing in atriums on other high-design spaces. The radiant panels were installed in the ceiling, and they were able to seamlessly integrate with the architectural ceiling feature.
CSE: What types of air balancing do you typically include in your designs? Describe an example.
Harwell: Since many of our projects involve renovating existing facilities and systems, a predesign test is a critical tool to confirm actual system conditions. A pre-TAB of the systems you will be touching allows a more accurate picture than just working from the original design values, and it can save you the embarrassment of insufficient static on the back end.
Hamilton: Air balancing is an integral part of all health care projects, especially inpatient hospitals. Our design process is to first ensure that all ASHRAE requirements are met in the design of the air-distribution system. For critical spaces, such as operating rooms, isolation rooms, and protected environment rooms, it is also important to ensure that your building is positively pressurized when compared to the outside. This will prevent colder air from entering the building through doors in the winter and from escaping in the summer. The testing and balancing contractor will also need to adhere to the specifications to ensure that your building is properly balanced.
Fuks: Air balancing is required for every HVAC project, but it’s most important prior to construction in renovation projects for existing facilities. We require the installing contractor to provide existing air readings at registers, main duct take-offs, and even at air-handling equipment to fully understand the available airflows and pressures prior to beginning construction.
CSE: When working on these types of facilities, describe the HVAC ventilation system, which might include hoods, fire-suppression systems, or other specialized ventilation systems.
Hamilton: Labs and pharmacies in a hospital will require their HVAC system to have hoods for the handling of chemicals and specialized exhaust systems for the disposal of chemicals. Special fire-suppression systems are oftentimes needed for server rooms, where activation of a wet sprinkler system will cause lasting damage to important equipment. The MRI system will also have a specialized quench vent, which serves as a means to protect the occupants in case of a gaseous release. This vent provides an escape for cryogen straight to the outdoors.
CSE: How have you worked with HVAC system or equipment design to increase a medical building’s energy efficiency?
Flanagan: HVAC systems serving existing health care facilities, especially large facilities, are subject to frequent changes in connected loads. As retrofits are executed to improve patient care and the patient experience, the HVAC systems need to be set up, managed, and measured frequently to maintain efficient performance. Often, efficient systems and equipment operate inefficiently due to lack of system balance, cross-connections, or a simple misunderstanding of system setup. It’s typical for us to perform system audits and facilitate measurement and verification of both air- and hydronic-distribution systems to reduce the energy consumption of a building. Reducing wasted energy has proven to be a more effective strategy for energy efficiency than promoting equipment replacement.
Kannady: One approach has been to develop a more distributed system approach, rather than reliance on larger central equipment. As many spaces in health care facilities have large air-change needs per ASHRAE 170: Ventilation of Health Care Facilities, a substantial amount of energy is used due to reheating. A distributed system approach leads to less reheating needs, but it also can increase the system’s first cost and make maintenance more difficult. A comprehensive discussion with the owner about system cost, efficiency, and maintenance requirements is necessary in the project’s planning stages.
Fuks: We have used heat-recovery technology more regularly including primary variable-pumping systems, magnetic-bearing chillers, and hydronic reset strategies to minimize the energy consumption of central utility plants, which are large users of energy on a medical campus. Also, air handling equipment is now mostly standardized on fan wall systems, variable-speed fans, low-pressure-drop filters, and supply airflow and temperature reset controls, to only use the energy needed to condition the building at that particular time.
Hamilton: With most systems that I have designed, I try to push the envelope as much as possible to ensure that the system is energy-efficient. Energy modeling is performed for almost all health care buildings that I have worked on. This usually gives me a benchmark so that I can test different energy-conservation measures to see which is more cost-effective and has an acceptable lifecycle cost. If the building is pursuing LEED, especially since the installation of version 4, the energy requirement is aggressive and will lead to a very energy-efficient HVAC design. Some of the examples of energy-efficient system design are fan arrays for air handling units (AHUs), electronically commutated motors for fan arrays in AHUs, variable frequency drives for most fans and pumps, static-pressure reset for AHUs, airside economizer for AHUs, runaround coils, and energy recovery for exhaust systems.
CSE: Describe a project in which you specified a specialty piping, hydronic, or pumping system for such a facility.
Flanagan: Health care facilities are complex. At the Center for Health and Healing, piping systems are used to move energy around the building, provide water to plumbing fixtures, collect drainage, distribute medical gas and vacuums to patient care areas, and provide fuel to equipment. Above and beyond all these typical health care-related systems, a rainwater-harvesting system captures, stores, treats, and supplies water to toilets and urinals throughout the facility. Further, the stored rainwater is used to provide radiant slab cooling at the main lobby.
CSE: What best practices should be followed to ensure an efficient HVAC system is designed for this type of building?
Jones: Significant gains in energy efficiency can be achieved by the use of decoupled systems. It is significantly more energy-efficient (and space-efficient) to pump water throughout a facility than air. Whenever possible, consider radiant heating and cooling or chilled-beam technology. Clearly, the hydronic portion of the overall system cost will be higher, but this can be offset by extreme reductions in airside system sizes and the volume of sheet metal. Once energy savings are added to the equation, any remaining overages can often be overcome with a quick payback.
Harwell: Above all, simplicity of operation and maintenance. The primary energy waster we see in existing operational systems is the result of dysfunctional systems made so by post-construction modifications and overrides. These are often avoidable through a more thoughtful and simplistic design with the operational staff in mind.
Fuks: Prior to beginning a design concept, sit down and discuss system-performance expectations and costs with the owner and/or operator. This alignment of expectations will set up your design for success. Also, always bring forward the latest and greatest technologies that have been proven to be reliable and cost-effective. Health care facilities invest in HVAC systems with longer lifespans than those in typical commercial projects, so it’s crucial they start on the right path with systems that can stand the test of time.
Hamilton: Some best practices for designing energy-efficient health care systems include:
- Perform energy modeling as early as possible, in the schematic phase of the project.
- Perform lifecycle cost analysis to select energy-conservation measures.
- Rightsize all equipment.
- Work closely with the architect to define the appropriate building envelope for the climate.
- Establish a baseline EUI and ensure the final energy model is at least 30% better than that baseline.
- Make sure the control sequence is clear, accurate, and designed to ensure efficient system operation.
- Ensure users are properly trained to operate the high-performance system as designed.