- Edward Clements, PE, LEED AP, associate vice president, HGA Architects and Engineers, Minneapolis, Minn.
- Ron Edwards, PE LEED, director, JBA Consulting Engineers, Las Vegas
- John Gautrey, PE, partner, IBE Consulting Engineers, Sherman Oaks, Calif.
CSE: What engineering challenges do performing arts centers (PACs) and museums pose that are different from other structures?
Edward Clements: Mechanically, there are significant challenges in designing both types of facilities. Foremost, an understanding of the intended use of the space(s) both now and 20 to 30 years down the road is needed. For example, a museum may not currently accommodate traveling exhibits but might have aspirations to do so. The most economical time to provide the systems that address this need is during the initial construction. For PACs, the types of performances—music, dance, theatre—can have an impact, but one common denominator is that of superior acoustics. The presence of perceptible or objectionable mechanical noise in an auditorium is something that must be avoided at all costs. If the systems don’t function properly, and quietly, the audience experience is diminished, and the hall will not meet the revenue projections that helped it be funded.
Ron Edwards: PACs usually have low preferred noise criteria (PNC) requirements due to the space acoustic criteria. We have seen ranges from PNC-15 to PNC-35. This results in low ductwork air velocities and large cross-sectional ductwork areas. This creates a challenge to incorporate the distribution ductwork into the architectural schemes which typically have ornate layouts and details. The solution involves creative out-of-the-box thinking between the mechanical engineer, architect, and acoustician.
John Gautrey: Both these types of building I find are more aesthetically driven than other types; however, they both require high degrees of technology and a sophistication of system design to be integrated into this aesthetic. We want the systems to perform but to be invisible. This provides both a spatial challenge as well as a technical challenge. The challenges are slightly different, however. The PAC has an acoustic performance overlapping the aesthetic, which results in overly large pathways needing to be developed while maintaining noise-producing equipment as far away as possible. If this is not considered during the planning of the building, then it is really too late to effectively handle this coordination. This acoustic overlay affects all systems, from mechanical and plumbing to low-voltage and electrical. The number and size of the electrical systems result in conduit bundles that can be equivalent to large air ducts; these must be coordinated in design, and not have to rely on the contractor to establish pathways during construction as other building types would.
CSE: How have the needs and characteristics of PACs and museums changed in recent years?
Clements: There has been a greater emphasis on energy conservation and sustainability than ever before. Traditionally, these building types, with their strict environmental criteria, have been overlooked in the conservation discussion. As it becomes more and more expensive to condition buildings, and as the public becomes more aware of the need to incorporate sustainable concepts into the built environment, these facilities must perform well, environmentally but also in energy performance. California State University—Northridge (CSUN) Valley Performing Arts Center (VPAC) in Los Angeles recently received LEED Gold certification—a testament to the sustainability that was included in the building’s design and construction. Great care was taken to include as many sustainable features as possible while still working to meet a set budget for the project. By all regards, it has succeeded.
Gautrey: Increasing technological integration has lead to ever-greater amounts of power and data being incorporated into the building, which provides an increasing challenge to coordinate. These buildings are considered high energy users. While energy efficiency should always have been considered, the onset of LEED and carbon footprint metrics has led to alternative strategies being considered for systems.
CSE: Please describe a recent PAC or museum project you’ve worked on—share challenges you encountered, how you solved them, and engineering aspects you’re especially proud of.
Edwards: JBA Consulting Engineers recently completed the design of a historic 2000-seat theater renovation in the New Orleans French Quarter District. As we started our analysis, it was concluded due to many factors that we would implement an under-floor air distribution system in lieu of continuing with the original overhead air distribution scheme. However, we did not have adequate room to install the vertical supply ducts which serve the under-floor plenum. The solution included distributing cooler air than required, thus reducing the quantity of air and the size of the required duct shafts. To reheat the air so not to overcool the occupants, sound-attenuated transfer fans which transferred space ceiling plenum air to reheat the supply air were added. This solution allowed for the temperature control required by the occupants and limited disruption to the historic architectural building features.
Gautrey: IBE is currently working on a Class AA art museum that will be housed in an existing print works, which is also being added onto. The building is currently un-insulated with tight floor-to-floor heights. We are upgrading the façade to incorporate continuous insulation and vapor barriers to avoid thermal bridging. Floor-to-floor heights are very limited, and underground trenches are being incorporated to distribute supply ducts from remotely mounted zone controls. The trenches also act as return air plenums and electrical distribution ways. Art walls are double thickness to allow vertical distribution of air and also house power and control panels for each gallery. All terminal controls have been mounted in mechanical spaces to permit maximum accessibility for maintenance. The tight floor plate has led to careful integration of MEP spaces and distribution to maximize the use of unutilized volumes.
Clements: VPAC opened in January 2011. The 168,000-sq.-ft. facility includes a 1,700-seat auditorium conditioned with an energy-efficient displacement ventilation system. Not only does this system provide an optimal indoor air quality environment for patrons, but background noise level has been measured at NC-20-23 in its first season. By comparison, a well-designed movie theater or quiet conference room measures NC-30. Both NC and RT are on par with some of the best performing arts venues in the world.
CSE: What cutting-edge energy-efficiency projects have you worked on at a PAC or museum recently? What design aspects were included?
Gautrey: The Water + Life Museums, Hemet, Calif., included high integration of renewable energy sources, particularly PV to maximize energy production in a desert environment. This was the world’s first LEED Platinum museum.
Clements: At VPAC we used displacement ventilation and demand controlled ventilation (varying the outdoor air delivered to the space based on the carbon dioxide level in the space—only enough outdoor air is delivered to provide adequate ventilation for people actually in the room, rather than just providing a fixed rate, which is more typical). For Northrop Auditorium at the University of Minnesota, we have designed a 100% outdoor air energy recovery system with chilled beams serving the back-of-house areas to optimize building energy use and work within the tight confines of a 1920s building not previously air conditioned.
Edwards: JBA recently completed the design of a 2,200-seat LEED Gold PAC with three seating levels, each with side balconies. The supply air for the entire hall was provided via under-floor air system. The owner’s intent included 100% occupancies during performances, but also having performances with as little as 20% to 30% occupancy (i.e., school children). It was determined with this occupancy profile individual temperature control zones throughout the seating area would be required. Each zone needed the ability to reduce its airflow and modulate its temperature independent of other zones. This controllability would allow for the required temperature control as well as energy conservation.
Automation and controls
CSE: What factors do you need to take into account when designing building automation and controls for PACs and museums?
Gautrey: They are a little different, as a museum is generally maintaining very tight and stable conditions for the most part with a fairly consistent internal load profile, while a PAC has very concentrated loads during a short period of time and very small loads the remaining time. The systems must be able to accommodate these changes. Museum controls must be robust and accurate with redundancy and cross-checks available. PACs are large-volume spaces, so they require multiple averaging sensors to provide adequate control. For both, it is necessary to consider placement of terminal controls not only for aesthetic reasons, but also for interaction with surrounding elements that may provide interference in the reading. The ability to reset for energy saving is critical to both project types. The museum is generally humidity sensitive and the PAC is temperature sensitive, which makes the control logic somewhat different. It is therefore critically important to provide very clear and concise sequences, as standard industry control setups do not work in either of these facilities.
Edwards: Whether it is a theatrical production or the temperature control of an under-floor air system which serves the high end seating, the speed and controllability of the control elements are critical. To provide these elements, the correct components need to be specified and the design needs to be understandable. In our current world of designing for green, we have sometimes created systems where the end user cannot understand how to operate the system. We need to keep it sophisticated but simple.
Clements: The single most important factor and one which often gets overlooked is that the controls systems must be tailored to the people actually operating the building. The most sophisticated system in the world can only operate that way if the building operator understands the tools at his or her disposal and how to use them. To that end, it is absolutely critical that the engineer discuss the systems’ design with the building operators so that they understand both the intent and the ramifications of modifications they may make. These could be energy use change, indoor environment change, and even occupant safety changes, especially if pyrotechnics displays are used in a performing arts facility.
CSE: When re- or retro-commissioning control systems in PACs and museums, what challenges do you encounter, and how do you overcome these challenges?
Gautrey: Accuracy and placement of devices is typically the biggest issue. This is easier to handle in a PAC being that it is primarily temperature driven, which permits use of wireless technology. This is not available for humidity sensors at the level of accuracy required, which provides a challenge of integrating placement. Nearly always, the control sequences have shown to be inadequate for maximizing energy performance, while maintaining control tolerances. A lot can be accomplished merely by re-engineering the sequences with components already in place.
Codes and standards
CSE: How have changing HVAC, fire protection, life safety, and/or electrical codes and standards affected your work on such structures?
Clements: The changing code requirements and associated solutions for auditorium exiting, elevator lobbies, areas of refuge, and high-rise buildings have impacted many of our projects. There are always solutions, but often at the cost of both budget and square footage.
Edwards: PACs usually have a large number of occupants, and the codes are requiring more outdoor air but at the same time less energy usage. We have completed studies on when it is appropriate to implement energy recovery systems thus implementing both of these items. The tipping point revolves around the yearly hours of operation and when during the year the hall is used. This allows for a lifecycle cost (LCC) analysis to be completed. With the LCC and initial cost estimates, the owner can be presented with a recommendation supported with associated costs and savings.
Gautrey: I do not believe that they have had a significant impact on the way I would approach the design of these buildings. However, the increasing focus on energy (whether from cost- or sustainability-driven goals) has changed the types of systems that are considered for integration.
Electrical and power
CSE: What’s the one factor most commonly overlooked in electrical systems in PACs and museums?
Clements: We have found that accommodation for temporary power is among the most overlooked electrical items. During programming and design, critical electrical needs are typically well defined and accounted for. However, as the facility takes shape, the owner can quickly envision new and unique special events and presentations occurring everywhere. Often the first test for this is at a hard-hat concert, or high-profile opening. The trick is to economically plan for some additional infrastructure to avoid makeshift digital media or cords and cables draped across the floor. Architects and engineers can help owners brainstorm and plan for the most likely scenarios.
Gautrey: In my opinion, the space required to run power and cabling systems is not adequately considered. It is important that these spaces be sufficiently flexible to accommodate change over time.
Edwards: These facilities typically have sound systems that require appropriate isolation from the remainder of the building systems to ensure proper sound quality. Additionally, harmonic conditions must be addressed due to equipment/systems that provide harmonic content.
CSE: What types of electrical products do you most commonly specify in a PAC or museum, and why? Describe the UPS system, standby power, generators, and so on.
Edwards: JBA normally has generators and UPS systems in facilities of this type. The UPS systems typically provide power to production-related data systems, including show control, lighting controls, SVC controls, automation systems, and so on. These systems are usually rather small in size and quite often dedicated to the specific system they supply. Diesel electric generators are typically provided to supply emergency systems, legally required standby systems, as well as optional standby systems.
Clements: Emergency generators are required for life safety in venues with large seat counts. They are also needed in arts centers and museums to keep security systems, vibration controls, and temperature and humidity controls running 24/7 to protect the collections and exhibits. UPS power is rarely required for museums and PACs, except in computer rooms. As far as installation, attention was paid to isolating dimmers, sound equipment, and transformers so as not to transfer noise into the hall. LED lighting was implemented for exiting in lieu of noisier ballasts.
CSE: How have sustainability requirements affected how you approach electrical systems?
Clements: It has affected our lighting selections. It has also affected how we approach the routing of infrastructure, and therefore the interdisciplinary coordination that is required. There has always been a need to be efficient and cost effective, but with more focus on the environmental impact of building materials, and the increased cost of precious metals, there is more pressure to thread the systems through increasingly tighter conditions.
Edwards: Upfront planning prior to progressing with detail design is generally necessary. Determination of energy allowances, equipment selections, as well as system control and monitoring is critical to sustainable design.
Gautrey: I am not sure that they have in any significantly different way from how we approach any other building type. Lighting sources, such as low-mercury lamps and LEDs (as color rendition improves), are helping to reduce energy use.
CSE: Have you had experiences with photovoltaic (PV), wind turbine, or other renewable energy projects at a PAC or museum? If so, describe it.
Gautrey: Yes. The Water + Life Museums have a large PV array integrated into the building. We have found that more recently, buildings are being set up to be PV-ready so that third-party agreements can be set up at later dates. We have not integrated wind, because site conditions did not permit it or the scale was not large enough to be economically feasible. Multiple small turbines have high infrastructure costs and low energy output.
Fire and life safety
CSE: What trends, systems, or products have affected changes in life safety systems in PACs and museums? Please include clean agent fire suppression systems, notification systems, and so on.
Edwards: Over the last several years, and even decades, there have been substantial advancements in the field of fire protection engineering. Technology is constantly evolving to meet the demands of the end user. In particular, air sampling smoke detection and clean agent suppression systems have become the norm for these types of applications.
Clements: Art galleries and museums have the challenge of providing fire suppression without damaging the collections. Over the years, best practices have been influenced by insurance requirements, lending institution policies, and by the particular materials of the art and artifacts. Halon, once favored, is not environmentally safe. Dry pipe and water mist systems have limitations. Clean agent suppression is good for unoccupied archives but not for actively used spaces. Recently we have been relying on incipient smoke detection along with a pre-action system to give the owner the greatest likelihood of avoiding a catastrophic event.
CSE: What fire/life safety lessons have you learned on past PAC and museum projects?
Gautrey: Discuss with fire marshals early and keep them involved in the decision-making process.
Clements: Multistory grand lobbies have become a given. And current codes make it onerous at best to avoid having them designated as “atriums.” The ultimate fire/life safety solution may not be decided until late in the project, but the design team needs to identify the possible mechanical, electrical, and architectural implications early on.
Edwards: Each project is different, and no system can just be copied over from one to the other. The engineer has to take a performance-based approach to each project when designing the detection and suppression system to ensure proper performance and client satisfaction.
CSE: What are some important factors to consider when designing a fire and life safety system in a PAC or museum? What things often get overlooked?
Gautrey: Response time of systems is a consideration, as it is usually not desirable to have the systems go straight to emergency mode, so some degree of time delay is required. Thus, pre-action and dry pipe systems are common. More recently, the evolution of VESDA (very early smoke detection apparatus) systems, which are especially applicable to museums, to analyze the contaminants in the airstream are being introduced to satisfy this delay and focus the response of the emergency system. Usually a big issue is the location of the fire control panel, as the responders want it visible and in a prominent location, whereas the aesthetics dictates a hidden location.
Edwards: The contents and the geometry of the space tend to be the biggest factors when designing a system, both detection and suppression. If the contents are highly sensitive, an air-sampling detection system may be desired for early detection. Likewise, if there are some valuable materials that a traditional sprinkler system would damage, then a clean agent system will be designed.
Clements: I polled my team, and a common response from both architects and engineers was the location of devices. Both museums and PACs put a high premium on aesthetics and visual context. Poorly placed notification and detection equipment, lights, and devices are detractions to exhibits and distractions to performances. For these buildings it is important to make the extra effort to identify appropriate locations for these items. New LED step lights can be extra bright, so they may also need special attention.
CSE: What specialized fire/life safety systems products have you specified on museum projects? How do you ensure sensitive artifacts are safe from fire while not damaged by fire protection systems?
Clements: Again, recently we have been relying on incipient smoke detection along with a pre-action system to give the owner the greatest likelihood of avoiding a catastrophic event. Unfortunately, many museums are also requiring system replacements or upgrades. This will continue as new technologies are developed.
Edwards: Air-sampling detection is typically specified for early detection. Clean agents are specified to ensure the artifacts are not damaged.
Gautrey: Pre-action and dual signal (heat and smoke) activation of fire/life safety systems are becoming normal, and in critical areas (such as archives), VESDA systems are starting to be introduced.
Mechanical and plumbing systems
CSE: What unique requirements do HVAC systems in PACs and museum facilities have, and how have they changed in recent years?
Edwards: PACs generally have many people grouped together on a single level or multiple levels, which requires large amounts of air to condition the space. The computer technology over the recent years has allowed us to utilize computational fluid dynamic (CFD) modeling to simulate temperature and air velocity profiles. This allows us to work with the designers to determine temperature and air velocity concerns early in the process and make the modifications when it is simple, as opposed to down the road when much effort has been expended by the design team and owner approval has occurred.
Gautrey: Museums require very tight tolerances for controls—more so than almost any other building. Temperature and humidity profiles in spaces must be maintained almost flat over the height of the display area, which requires fully mixed air systems. This makes placement and selection of outlets critical as they must be integrated into an architectural aesthetic in a sensitive way. It is interesting that these tolerances seem to be getting tighter when most research would suggest they have been overly stringent at great cost, both in terms of initial setup and continued operations. It will be interesting to see if this trend changes and conditions are relaxed as costs continue to escalate. For PACs, I think really it comes down to a coordination issue. The acoustic requirements dictate much slower air speeds and larger ducts than would typically be utilized in other building types. Routing and location are also very important, as you do not want a beautifully quiet space that resounds in water noise every time it rains or a bathroom fixture is flushed. These considerations are amplified in a PAC beyond other building types.
CSE: Describe the use of fans and ventilation equipment in a recent PAC project.
Clements: Northrop—a similar distribution system has been incorporated in this hall, seating 2,800 people. The primary difference is one of scale. Since there are more patrons, the supply volume has been ramped up to 62,000 cfm. The air handling unit for the auditorium houses 12 variable speed supply and 12 variable speed return fans. Fans can be staged on and off to match the capacity generated at the air handling unit with the need in the space even more closely than would have been possible with one or two supply fans, which would be traditional in an air handling unit of this size. Both projects incorporate sophisticated exhaust systems to aid in stage productions that include fog effects. Rather than having the fog roll off into the audience chamber, it is removed through the ventilation system without disturbing the patron.
Gautrey: Menlo-Atherton PAC utilizes an under-floor plenum to distribute air to the audience chamber. Central air handling units are located remote from the chamber and supply very low velocity air to the space. Balconies are zoned separately from the main floor to permit adjustment of airflow to stratification mixing.
CSE: When working in museums or facilities with delicate artifacts, describe the systems you specify to deal with relative humidity, ventilation, and other issues.
Clements: Temperature and humidification must be tightly controlled to avoid rapid fluctuations in the environment to which artifacts are exposed to avoid damage to them. Particulate filtration is a common concept, but gas phase filtration is equally important. Removing gaseous contaminants from the air within a museum can substantially improve the life of the stored artifacts and potentially allow them to be displayed in an open environment rather than within a display case.
Gautrey: Ventilation is typically introduced in a central air handling unit, but in reduced quantities based on carbon dioxide sensing of zone requirements. This results in minimizing fluctuations in humidification requirements. Economizers in most climates typically prove to be uneconomical, as the humidity control restricts their use to all but a few hours. Ventilation quantity should be back-checked against building pressure/exhaust quantity to ensure that correct pressurization is maintained for control of moisture buildup in the building fabric. Humidity, in my opinion, should be introduced via steam to minimize absorption length. The steam should be clean of chemicals whenever possible and generated centrally for long-term efficiency. Rough control is handled centrally at the AHU with terminal humidifiers providing precise control of individual spaces.
CSE: Describe the acoustics requirements in a recent theater or PAC. What issues did you encounter, and how did you resolve them?
Edwards: The PACs I have been involved with all require a maximum PNC. This calculation, typically completed by the acoustician, is highly dependent on the space humidity levels and the reflectivity of the room surfaces. I have designed halls with and without controlling the minimum humidity levels, and they both can work well. However, as sound waves travel better in moist air, acousticians prefer to have a minimum humidity level of approximately 30% to 40% relative humidity. In some parts of the country, like the Southwest, maintaining these humidity levels is costly from initial construction to continued operations. The design team must coordinate the best solution from maintenance and cost position and present the alternatives to the owner for discussion.
Gautrey: We are currently working on a theater for San Francisco State University with extremely complex geometry, and located in an environment where utilization of the natural conditions permits significant energy savings. Natural ventilation is proposed for several back-of-house spaces and lobbies, removing what could usually be considered one layer of acoustic protection for the hall. The hall itself is, therefore, treated as a separate acoustically enclosed volume. Air, water, and power systems are remotely located in a central facility area, removing the noise source from line-of-sight to openings into the building. Air is introduced by floor plenums. Distribution of air from central utility plant is via subterranean airways that are fully accessible for cleaning and replacement of acoustic treatment. The length of airway obtained by this distribution strategy along with the integration of plenums and bends prior to duct entering the occupied space allow mechanical noise to be attenuated remotely and without the addition of sound traps, which increase system pressure and therefore energy use.
Clements: At VPAC great acoustics was one of the client’s top goals. Our acoustician, architects, and engineers immersed themselves in investigating all cost-effective options that could still achieve acoustical goals. For seismic and cost reasons, a steel structure with bracing was selected in lieu of concrete. This impacted mechanical duct routing, sound isolation, and penetration details. Plumbing pipes required additional chase construction to isolate water noise. Concrete tunnels were able to be formed in the foundation to provide air distribution to the floor of the auditorium and the lobby.