Operating on medical and hospital projects: fire/life safety and HVAC
Engineers tasked with working on hospital and medical campuses find themselves tackling unique challenges: evolving technology, increased specialization, and maintaining operations while under construction. Here, professionals with experience on such facilities share advice on how to finish projects that report a clean bill of health for HVAC and fire/life safety.
Larry Anderson, PE, RCDD, CDT, Principal, TEECOM, Oakland, Calif.
Jeremy Jones, PE, LEED AP, EDAC , Healthcare Market Leader, Affiliated Engineers Inc., Chapel Hill, N.C.
Daniel S. Noto, PE, LEED AP BD+C, Healthcare Studio Leader-Southeast Region, exp, Atlanta
Eric Reuther, PE, LEED AP BD+C, Principal, McClure Engineering Associates Inc., St. Louis
Jonathan B. Slagel, PE, LEED AP, HFDP, Principal/Vice President York Office & Healthcare, Barton Associates Inc., York, Pa.
Bill Talbert, PE, BEMP, LEED AP, Senior Mechanical Engineer, MEP Associates LLC, Verona, Wis.
CSE: Describe unique security and access control systems you have specified in hospital or medical campus projects.
Jones: Our major challenges in security and access control often result from the competing interests of patient safety and patient security. Two examples that come to mind are behavioral health and infant protection. First, in a behavioral health facility, patients are often confined behind locked doors both for their protection and the protection of the staff caring for them. Thoughtful design must be given to the function of that physical security during an emergency, such as a fire. If the code requires a pull station in an area to which behavioral health patients have regular access, can you responsibly install it? Do all doors immediately open if the fire alarm system is activated for any reason? There are significant dangers either way. The appropriate compromise almost always involves some type of delayed egress, but this takes significant understanding and buy-in by both the owner and the AHJ. In the second scenario, unfortunately, infant abduction is a concern anywhere infants are present. Multiple levels of infant tracking and additional security are required to prevent this atrocity. If all security doors immediately open when a fire alarm pull station is pulled, a potential criminal could exploit that fact. At the same time, easy exit is required during a legitimate emergency. Similar to behavioral health, delayed egress is almost always the solution, but this adds risk.
CSE: What are some of the commissioning challenges for proper alarm signaling for hospital or medical campus facilities?
Reuther: The engineer needs to understand where the fire and smoke barriers, partitions, and walls are located in the building. This often requires a conversation with the architect to help identify these as the International Building Code (IBC) defines them since all of the life safety damper requirements are based on the requirements from the IBC. Due to the I-2 building occupancy, hospitals often require a lot of combination fire-smoke dampers, which involve coordination with both the architect to locate shaft walls to install them in, as well as the electrical requirements associated with the dampers.
Jones: The primary challenge is that these systems are tested so often, for completely legitimate reasons, that there is a real danger of a never-cry-wolf scenario. How often have you heard a fire alarm in a hospital and truly felt in danger from an actual fire event? I'll admit that I am exposed to these tests more than the average citizen, and if you're like me, the answer is "not even once." Announcements can be made to ignore such alarms for a time, but that creates a risk in the event of an actual fire. It also contributes to occupants' tendency to ignore all alarms. At the same time, if you never test these systems, how do you know they will work when needed?
CSE: Have you specified distinctive HVAC systems on any hospital or medical campus projects? What unusual or infrequently specified products or systems did you use to meet challenging HVAC needs?
Reuther: One unique system was a cooling system for emergency generators. The cooling towers were sized to pick up the additional heat from the generators. We designed a separate glycol-cooling water system that took heat off the jacket water from the engines and then was pumped through a plate-frame heat exchanger that was tied to the condenser water system. This was all done to avoid the large building openings to allow for the airflows required by a typical generator radiator fan. The duct silencers that would have been required to keep the generator noise inside the building were going to be too large to accommodate in our building footprint.
Jones: I've mentioned active chilled beams a number of times within these responses; we have successfully implemented this system in numerous health care settings and are fully comfortable with continuing to do so. We also have implemented heat-recovery chillers to help mitigate health care's inherent simultaneous heating and cooling dilemma. Geothermal and water-source-rejection methods have been implemented where climates and physical locations allow. Aggressive energy goals and code requirements are going to continue to push the industry in the right direction.
CSE: Have you specified variable refrigerant flow systems (VRF), chilled beams, or other unique HVAC systems into a hospital or medical campus building? If so, describe its challenges and solutions.
Reuther: We have used some variable refrigerant flow (VRF) systems in a few smaller medical office buildings. They can provide a good alternative to typical direct expansion (DX) systems because multiple zones can be achieved off a single outdoor unit. Furthermore, they provide energy savings by sharing load between zones. In the larger hospitals, we haven't found these systems to be as applicable because there are typically large chilled water systems already existing in the facilities.
Jones: On our Moses Cone North Tower expansion project, we designed the patient rooms with active chilled beams. Our preliminary energy modeling indicated a 39% energy savings as compared with traditional variable air volume. Our savings estimate has proved to be accurate over the initial 2-year history. We also have seen a tremendous reduction in patient temperature complaints, when compared with their previous patient rooms. They have a tendency to collect lint, but we have found that to be manageable by using a portable HEPA vacuum and tracking time between the cleaning of each beam.
CSE: What unique HVAC requirements do such projects have that you wouldn't encounter in other projects?
Reuther: Space humidity is critical as there are a handful of rooms in a hospital that are typically designed for lower temperatures while still keeping the relative humidity below 60%. Another unique requirement is redundancy. Many of these systems cannot afford to be shut down, so the designer needs to have a backup planned into the system to allow for equipment to be serviced. Lastly, due to the fact that the hospitals typically need to stay functional throughout the construction, we find ourselves often looking for creative ways to phase projects in order to limit the impact on the department functionality. Many times when designing AHUs, we will provide spare capacity and tie two units together in order to allow for a space to be fed from two different systems. This often comes in handy during renovations.
Noto: Lower temperature set points, more strict humidity-range control, and higher airflows are all components that distinguish health care projects from other types of projects.
Jones: The process of updating code language to apply to new technologies is notoriously slow. At the time when the active chilled beams were designed for the Moses Cone project, our applicable codes weren't ready to specifically allow or disallow this system. Even though North Carolina is not subject to ASHRAE 170, Addendum H hadn't yet been issued, which would have at least given us a precedent to stand on. Our patient rooms' active chilled beams receive 2.25 air changes of filtered and conditioned outside air, with a total air-change rate of 6. We were able to get this approved because North Carolina's state-specific health care licensure rules only require two total air changes. We didn't have to debate filtered versus unfiltered air changes because we fulfilled the requirement with filtered outside air.
CSE: When retrofitting existing facilities, what challenges have you faced and how have you overcome them?
Reuther: We had a pair of AHUs installed in about 1950 in the basement of a hospital that had numerous additions built around them. The owner had avoided replacing these units for years as there was no simple way to get the equipment in or out of the mechanical room due to all of the surrounding additions. In addition, these AHUs were feeding several critical areas that could not go without HVAC for any length of time. Ultimately, we helped the owner develop a plan to replace these AHUs as well as one other older unit in a series of AHU replacement projects. Starting with one new unit on the roof, we freed up enough capacity on one of the existing units to shift loads from one to the other. We shifted loads between new and existing units until we reached the final product. At the end of the day, the hospital had four new AHUs scattered around the hospital between three different mechanical rooms and one rooftop unit. The replacement unit in the 1950s section of the hospital had to be completely disassembled by the contractor down to the panels, coils, and a fan, which were all snaked through the hospital and re-assembled in the mechanical room. All three of the older AHUs were replaced without any space having an HVAC outage of more than 4 hours at a time, which was just used to make duct tie-ins after-hours.
Slagel: Renovating or retrofitting existing hospitals can be one of the most challenging projects for an MEP designer. In most cases, the MEP systems and equipment that serve the project area also serve other spaces adjacent to the project, which must be maintained in operation during construction. When our teams encounter these projects, we first and foremost engage the owner in the discussions of project scope and phasing. It is critical that system downtime or service disruption be planned with the hospital's facility and engineering staff and affected clinical departments to ensure that necessary backup and contingency plans are in effect for patient and staff safety during the project. In some cases, it is necessary to include temporary service equipment (e.g., air handlers, generators, etc.) to provide service to operational areas where upgrades/replacement of critical MEP equipment are taking place. We have found that it is extremely important to have these discussions and planning processes very early in the project design phase so impacts to project phasing can be openly discussed and accounted for by the entire project team.
Noto: Finding accurate existing-condition drawings and finding the time to verify them are usually very difficult tasks within an existing, running hospital. Coordination for access to the space is very important.
Jones: Overhead space constraints and existing system-capacity limitations are two common challenges. We recently ran into the challenge of an existing clinical laboratory in which equipment had been continually added to the space over the past 20 years. The result was a space that could not keep up with the heat load. The laboratory was landlocked within the facility, with no additional space above the ceiling, which prevented us from just throwing more air at the problem. Again, chilled beams were our solution. They are perfect for dealing with high sensible loads, and since water is so much more efficient at energy transfer than air, their infrastructure fit easily above the congested ceiling.
CSE: When addressing indoor air-quality issues, what best practices or tips do you have for other mechanical engineers? Describe air-change rates, particle concentrations, humidity, and other issues.
Reuther: When designing a room where the humidity level is critical, I'd recommend designing a little bit of safety into the system's capacity. I often see the design matching the room requirements with no wiggle room. For example, operating rooms (ORs) designed for 65°F, 60% relative humidity (RH) and the occupants are upset when the room is at 65°F, 62% RH. If the occupants cannot accept a humidity above 60% (very common in ORs), then the designer should be providing equipment that can exceed this requirement. There are too many factors that can produce a scenario where the system is operating above the design point (i.e. weather phenomena, filter loading, dirty coils, sensor inaccuracy, special circumstance in space, etc.).
I would also recommend that engineers pay attention to air distribution in the room. The goal is to keep the cleanest air near the patient's breathing zone and pull contaminants away from the patient. While this typically is done well in an OR, this is often overlooked in other spaces like patient rooms.
Another important thing to pay attention to is pressurization. While the codes simply state whether a space is supposed to be positive or negative, it is unfortunately not that simple. What if you have two positive spaces next to each other? Which way should the airflow go? The reality is that the hospital has a wide range of pressure gradients that flow air from the cleanest to the dirtiest spaces. The designer really needs to understand the flow throughout all the spaces.
Lastly, I can't stress the importance of humidity control enough. Because so many spaces are being maintained at colder temperatures, the potential for higher humidity levels increases. This is obviously dangerous as higher humidity levels can lead to mold growth. While mold is always a bad thing, it is especially scary in a hospital environment where you have patients with compromised immune systems. HVAC systems must be designed to limit humidity levels from getting over 60% RH. This often includes limiting adjustment on thermostats so that space temperatures cannot be set lower than the design numbers.
Slagel: In addressing or, better yet, preventing indoor air quality issues in health care occupancies, it is important to focus not only on the specific space in question but also the adjacent spaces and overall building layout and construction. In many instances, air quality issues related to temperature and humidity are created by conditions present in adjacent spaces or the building construction. It takes a holistic approach to solve and prevent these issues. For example, a critical lab space may require a specific temperature and relative humidity level be maintained 24 hours a day. If the room is not properly constructed with thermal and vapor barriers, conditions in the adjacent space(s) could negatively impact the HVAC system's ability to maintain design conditions in the target room. The successful design, construction, and operation of a critical environment space requires close coordination between the design engineer, architect, and constructor to ensure all variables are addressed and meet the requirements defined by the owner.