Ask an expert: Hospitals, health care facilities: HVAC
Health care facility designers are expected to keep pace with increasingly complex, advanced engineered systems and features
Boothe has more than 24 years of experience in the health care industry. As Principal/Senior Electrical Engineer, he has led numerous projects, including new greenfield hospitals and additions and renovations to existing health care facilities.
In his role as Vice Presidentand Health care Practice Director, Chrisman coordinates strategy for the company’s health care projects nationwide. His areas of technical expertise include fire protection and code consulting.
As Senior Electrical Engineer, Divine has spent 21 years in the consulting engineering field, with the past 17 years designing and engineering health care facilities. He is responsible for power, lighting and fire alarm design for hospital and health care projects.
As a founding Principal of Certus Consulting Engineers, Koppenheffer brings 24 years of experience in the MEP consulting engineering industry specializing in health care facilities. He has a range of expertise in mechanical and plumbing engineering.
As principal, Martin oversees multidiscipline engineering teams with a focus on national and international health care markets. He originally joined the firm as an electrical project engineer.
Phillips works with consulting engineers, customers and internal business development staff. He is responsible for educating them on the solutions offered through controls and building automation.
As Health care Team Leader in the company’s North Carolina Building Systems Division, Torres works with organizations such as Duke Health, UNC Hospitals and Rex Health care. He has been with RMF since January 2001.
As vice president and mechanical department head of Florida building systems for the company, Woods has played a key role in engineering mechanical solutions for major health care projects. She has facilitated sustainable design for several successful green building projects.
CSE: 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.
Woods: Simultaneous dehumidification and reheat to maintain space temperature and humidity control is a unique challenge that engineers face when designing health care facilities. As an engineer in Florida, our high dehumidification day requires some careful thought when considering the cooling demands. Cautious selection of equipment is required to ensure that the system is sized adequately for this peak condition.
Koppenheffer: A unique cooling system approach was employed to provide additional resiliency to a project using domestic water as a secondary cooling source. The project was located in northern Minnesota where Lake Superior was the source of domestic water with maximum temperatures not exceeding 46°F during summer conditions. The piping system and air handling equipment was designed to meet peak cooling loads with the domestic water. Under this approach the facility achieved an N+1 arrangement on the cooling system without the need for additional chillers or emergency power generation to power them during a loss of normal power. Special attention was required to design the system including water service calculations, cooling coil design and sanitary wastewater design to handle the peak flow rates under the emergency condition.
CSE: What unusual or infrequently specified products or systems did you use to meet challenging heating or cooling needs?
Martin: Active chilled beams are always a consideration for spaces in a health care facility where they are allowed by code. This is a technology we frequently employ for improved energy performance.
Koppenheffer: Temperature requirements in operating rooms pose several challenges. Maintaining lower temperatures while maintaining code required humidity ranges lends itself to strategies such as desiccant wheels and glycol loops. Finding a balance between dehumidification/sub-cooling and energy efficiency can lead to creative solutions. On one project, the surgeons requested the ability for “rapid warmup” of the operating room. Rapidly increasing the supply air temperature from the terminal box, introducing hot air into a cold room, will adversely impact laminar flow as the warmer air hangs at the ceiling level. Using computational fluid dynamic models and lab mock-up, it can be shown that the difference between the supply air and the room air should be maintained at no greater than about 15°F. Use of control strategies to slowly increase the reheat discharge temp over several minutes can warm the patient while maintaining laminar flow across the table. Radiant panels can be another strategy in this example. It is important to understand help the stakeholders understand that a request to “warm the room” really has a goal of warming the patient on the table and not the thermostat on the wall or in the return duct.
CSE: How have you worked with HVAC system or equipment design to increase a building’s energy efficiency?
Divine: We’ve used energy recovery equipment in medical office buildings with excellent results. Our hospital clients tend to avoid those systems, out of concern for cross-contamination of the airstream.
Koppenheffer: One strategy to increase the hospital’s energy efficiency is to employ operating room airflow setback. This strategy includes reducing the airflow to the operating rooms during unoccupied periods to reduce supply and return fan power, cooling energy power and reheat energy. The system included individual supply and return air venturi air valves for each operating room as well as control system integration to manage the occupied and unoccupied setting for the facility. Through the use of air valves, the airflow to each operating room is reduced during unoccupied periods by approximately 75% without compromising room differential pressure or ventilation requirements. On one project this strategy was shown to save just over $17,000 in electrical energy per year on a 20,000 cubic feet per minuteair handling unit.
Woods: Minimizing reheat is always the goal in health care facilities. Performing envelope optimization studies earlier in design is a very effective tool to ensure that a balance between the cooling and reheat load can be maximized. Although it is counterintuitive, a higher performing envelope can lead to higher overall energy consumption. An energy model should be performed as early as possible to help aid the design team in decisions regarding orientation and glazing types and applications.
CSE: What best practices should be followed to ensure an efficient HVAC system is designed for this kind of building?
Koppenheffer: One of the keys is to develop owner project requirementsat the onset and write a basis of designearly. Since design is an iterative process that will necessarily be adapted, evaluated and verified as the building design develops, assemble a team that can help with continuous pricing. Engage the entire team to evaluate all options, price throughout all stages and track through the process such that the decision is well-informed and both the total cost of construction and total cost of ownership are accurate and known.
Martin: Enhanced energy modelling should be performed throughout the design stages to help in the selection processes of high-performing HVAC systems. In addition, extra care needs to be given during the installation, balancing and commissioning of these systems.
CSE: What is the most challenging thing when designing HVAC systems in such buildings?
Torres: The challenge and, in my opinion, what makes designing HVAC systems for health care projects is the complexity of the building. Unlike other buildings (offices, classrooms, etc.) or projects, the design of the HVAC system requires an understanding of the required air changes, filtration requirements, pressure relationships and experience with understanding the medical systems being installed in a project. An experienced health care engineer understands what the true heat loads are for the equipment, defining the level of redundancy for the air handling units and exhaust fans and then implement these requirements within the define construction budgets.
Divine: My mechanical colleagues tell me that their most challenging designs cover multiple spaces with different pressurization requirements, in the same general area.
Koppenheffer: Three of the most challenging issues when designing HVAC systems for health care facilities include future-proofing, project budget control and coordination of the necessary medical equipment that will be installed. Future-proofing includes designing the systems to anticipate future expansions and improvements in technology as is the case for imaging equipment. It is imperative to engage the hospital team early in the design process to understand their future goals. With careful consideration, the system design can be augmented to include the ability for future change without costly modifications or replacement. One example would be the ability to add final filters to an air handling unit in the future so that it could be used for patient care space. Another example would be sizing the piping from a process chiller such that an MRI could be replaced in the future and existing services could be used without the need for replacement. In addition to future cost avoidance, employing these types of strategies minimizes downtime and impact on the operational hospital during future changes.
Martin: High performance HVAC systems require a high level of accuracy during installation and care must be given to the details. For technologies such as active chilled beams, something as simple as not paying attention to insulation installations can have a major impact on system performance.
CSE: What systems are you putting in place to combat hospital acquired infections?
Woods: Continual evaluation of filtration requirements, pressure relationships and airflow distribution is evolving in the industry to ensure that HAIs are minimized. Engineers should heed to this research and pivot as needed in their designs to ensure that the most current best practices are maintained to ensure that patient safety remains top priority.
CSE: Medical gases are vital for hospitals and medical campuses. Define the project, its goals, the challenges and the design solutions.
Koppenheffer: A recent project included the replacement of the bulk medical gas systems, including oxygen and nitrogen for an existing operational facility. The challenge was that the new bulk gas systems would need to be installed approximately 1,000 feet away and be routed underground to the existing facility through the labyrinth of existing underground services including chilled water, steam, natural gas, emergency electrical duct bank, storm and sanitary sewer and communications cabling. Through the use of BIM, the design was coordinated with multiple disciplines and utility providers to allow continued operation of the facility during construction. Once installed, each of the systems was changed over without a loss of medical gas service to the facility.
Torres: Design medical gases for an existing or new medical campus is defined by NFPA 99, Chapter 5 Gas and Vacuum Systems. The medical gas systems will be designed or retrofitted to be a Category 1 system as the loss of the piped gas would likely cause major injury or death of patient, staff or visitors. A larger challenge is designing medical gas systems for outpatient facilities as the designer needs to understand the goals of the facility, how the patient is treated and design if the medial gas system should be Category 1, 2 or 3. Each decrease in category comes with limitations to how the doctors can operate in the facility.