Sports, entertainment venues: HVAC systems
Participants (left to right):
Keith Cooper, PE, President, McClure Engineering, St. Louis
Douglas H. Evans, PE, FSFPE, Fire Protection Engineer, Clark County, Nevada
Bill Larwood, PE, LEED AP, Senior Vice President/Project Principal, Syska Hennessey Group, Los Angeles
Kevin Lewis, PE, LEED AP BD+C, Vice President, Henderson Engineers, Lenexa, Kansas
Bruce McKinlay, Principal, Arup, Los Angeles
CSE: What unique requirements do HVAC systems have that you wouldn’t encounter on other structures?
McKinlay: For sports venues, large quantities of ventilation typically are required to meet occupancy demands. In addition, there are significant latent loads from the occupants. These factors normally require air handling systems to be designed with both humidification and dehumidification. In addition, the systems are often used intermittently and are required to bring the house to setpoints quickly after the arena fills up and lights are turned on. Because of the large ventilation loads, there is significant opportunity to save energy through air side heat recovery from exhaust air streams. This is typically done through run-around coils, air heat exchangers, and heat pipes.
Evans: HVAC systems also may be designed to provide smoke management functions. This can substantially complicate the HVAC design. The designers must determine if it is more cost-effective to have a dedicated smoke management system, or if it should be combined with the HVAC system. In order to design the smoke management system, the expected fire size must be taken into account. If the design intends to keep smoke above head height to allow safe evacuation, this can further complicate the smoke management design.
Larwood: Arenas with hockey games must maintain air with low humidity, which can be tricky considering that these venues’ doors are continually being opened before and during the event. We’ve approached these venues by sub-cooling the air to less than 50 F to remove moisture and then reheating to maintain comfort. Of course, security continues to be a factor in the design of HVAC systems for sports and entertainment venues—the location of outside air intakes should always be considered to minimized chemical threats.
Lewis: The biggest issue in sports and entertainment venues is typically the size and location of the units. Depending on where the units are located, you need very large ductwork to supply and return air. You also need a close proximity to an outside wall so you can provide a louver with the capacity to bring in adequate outside air. In most conditions, we typically work with custom air-handling unit (AHU) manufacturers to be able to work around structural and head height limitations and still provide an energy-efficient solution. Because our units are custom, it gives us design flexibility to provide the necessary cooling/heating and bypass coils to meet the supply demands of multiple event types.
Cooper: Dehumidification and high latent loads become typical considerations in many of these facilities. Large and varied uses may dictate unique air distribution challenges. Ventilation controls must be able to accommodate large swings in outside air requirements often over relatively short time periods. Pools demand special temperature, humidity, and air movement controls. They also present opportunities for energy recovery and demand close attention to vapor barriers.
CSE: How do such venues vary from region to region?
Lewis: Different regions have different design conditions, and these need to be considered prior to the start of the design. For a predominately heating climate zone, it may not be the best idea to provide a VAV system unless you know that you can get good circulation of the air throughout the zone. It may be a good idea to design single-zone systems that can force the air throughout the space effectively. In warm and humid climates, you have to design with the heat and humidity in mind. In these zones it makes sense to have a way to treat the humidity the building may encounter.
McKinlay: The design of the air handling systems can vary significantly depending on the climate of a particular region. For example, an arena in the southeastern United States, where humidity is high, may need a dedicated system to pretreat outside air to provide tighter control.
CSE: What unique solutions in heating and cooling systems have you specified recently? What “unusual” HVAC systems have you offered as an option to clients?
Larwood: We’re seeing more attention being paid to high-performance building system features to reduce energy use. Due to the occupant density, sports and entertainment venues require significant amounts of outside air. With the use of air quality sensors, the use of outside air is minimized when there are extreme outdoor temperatures. Energy recovery is also a consideration—cooling the incoming outside air with the air being discharged.
Cooper: I’ve seen pool dehumidification systems, heat recovery chillers, low-temperature heating hot water systems, ventilation control systems, and locker room air transfer systems. We had a project where the domestic hot water boilers (nominally 140 F) were used as a backup source to create low-temperature heating water (nominally 125 F) for the 5 months each year that the campus turned off the steam boilers. Recognizing we had high-efficiency condensing domestic water boilers already in the project, we were able to use these boilers to provide the desired redundancy needed for the heating water system.
McKinlay: We proposed displacement ventilation under the seats for an open-air soccer stadium in the Middle East to keep spectators cool during the game.
Lewis: The trend in sports seems to be the use of VRF systems, which are somewhat unique in the fact that multiple AHUs are tied to a single condensing unit. In these systems the amount of refrigerant piped at any time is controlled by a variable frequency drive (VFD) on the compressor, which makes them very efficient under part load. When specified with the right options, these units can also have different AHUs in different modes. That is, one AHU can be in cooling while another is in heating. This increases the flexibility of the units and makes them very useful in a variety of situations.
CSE: Describe a recent HVAC challenge you encountered and how you worked to overcome it.
Lewis: The biggest challenges lately have been renovating existing arenas that don’t currently have existing air conditioning systems. In these types of situations we have been using laser scans to locate all existing pipes, conduits, and ductwork. We then add this information to the model and work with the architect and structural engineers to carve out a path for the ductwork with as little disruption to existing systems as possible. We have also designed unique return air systems where plenums are used in lieu of ductwork. This reduces the quantity of ductwork that needs to be routed through existing space and also saves money for the project.