As published by Consulting-Specifying Engineer
If you remember back to what your high school locker room was like, one of the first things to come to mind is probably the smell or what we would call bad indoor air quality. There were likely many things contributing to that smell, one of which was the heating, ventilation and air conditioning design.
The IAQ in sports training and fitness facilities can vary greatly depending on a facility’s age and level of competition among other factors. Retail fitness (strip mall spin or aerobics studios) and youth sports are more often going to have bare minimum HVAC systems resulting in fair to poor IAQ. As you can imagine, the IAQ expectations are much higher in professional and NCAA Power Five conference sports facilities.
ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality dictates that locker room ventilation is exhaust driven and training spaces are outside air driven. The minimum exhaust rate for locker rooms is 0.5 cubic feet per minute per square foot. The minimum OA rate for training spaces is 20 CFM/person with area rates ranging between 0.06 and 0.18 cfm/square foot depending on the occupancy category. Makeup air for locker room exhaust is not required to be 100% OA, so transfer air from adjacent spaces can be used as makeup. Retail fitness and youth sports facility designs are often first cost driven and will use the minimum requirements to stay within budget.
Typical systems designed to meet minimum ventilation requirements will include overhead exhaust grilles, either duct- or ceiling-mounted, connected to a constant volume exhaust fan for locker room ventilation. Locker room makeup air is often handled by wall or ceiling mounted transfer grilles with the primary conditioning coming from a recirculating type air handling unit. Training areas will most times be served by a recirculating type air handling unit providing code minimum OA. MERV 8 filters, the industry-accepted minimum, are often used in the air handling units with both the air handlers and exhaust fans cycling off at night when the building is unoccupied.
Some easily overlooked design considerations on budget driven projects — or any project for that matter — that negatively impact IAQ are building pressurization and mixing of different air classes. A building air balance calculation should be performed and OA flow adjusted to ensure a positive building pressure at all times.
If a building is allowed to operate negatively pressurized (i.e., more exhaust air than OA), then air will be pulled in through doors and cracks in the building envelope. This air is unfiltered and unconditioned which could both negatively impact IAQ and energy usage. Mixing of different air classes is regulated by code and should be avoided except under certain conditions as detailed in the code.
For example, air from a locker room (Air Class 2) returned to an air handler is prohibited from being mixed with air from offices spaces (Air Class 1) before being redistributed to spaces with an Air Class of 1. When designing to meet higher IAQ expectations, these pressurization and air class concerns are often inherently improved by the system types and strategies used.
Meeting client IAQ expectations in professional, NCAA Power Five conference and similar high-end sports and training facilities requires going above and beyond the minimums that code dictates. In an ideal world where cost and operations could be ignored, this would mean using 100% OA at a constant rate, which not only meets the space loads but gives great air turnover while exhausting all air supplied except what is needed for building pressurization.
The OA could even be cleaned before entering the building using HEPA filters and the latest contaminant-killing technologies. Certainty at this point the resulting IAQ could be as good if not better than the air quality outdoors.
However, the first cost, operating cost and maintenance required would be enough to take any client’s breath away. To avoid blowing budgets, a balance must be made between the client’s IAQ expectations, energy use and cost. There is also a point of diminishing return, where only marginal increases in IAQ are achieved, but cost and energy usage for those increases remain high as the graphic below illustrates.
As most IAQ strategies are implemented, there is an increase in cost and energy/carbon dioxide (known as CO2). At a certain point, strategies may yield marginal IAQ improvements but still have a high cost and increase to energy/CO2 (see Figure 1 below).
Some current strategies that strike a good balance between IAQ, energy use and cost include things like increasing ventilation rates, 100% OA air handlers with energy recovery, source capture, contaminant separation, building automation systems, increasing filtration and commissioning.
The list below highlights ways to improve IAQ with a primary focus on sports training and fitness facilities and is not intended to be an exhaustive list.
The above strategies for improving IAQ are frequently used in projects that cater to professional or collegiate athletes. However, any of these strategies can be scaled to fit most sports and fitness training facilities while keeping an eye on the budget. For example, 100% OA units can be paired with more cost-effective packed rooftop units or variable refrigerant flow systems. Properly planning for increased filtration at the start of a project can help keep impacts to cost down.
Commissioning, sometimes required by code, can be easily tailored to fit any project and even targeted at specific IAQ goals within a project. As these strategies continue to become more widely adopted across all facility types, the relative cost should come down making way for new technology to emerge.
Like any new technology going into buildings, the goal should be to improve the occupant and operator experience while reducing energy use. The same goes for new IAQ technology. Some newer technologies already on the market but not widely adopted include equipment disinfecting cabinets. These are cabinets where athletes put their equipment immediately after a workout to both disinfect and dry using ultraviolet lights or ozone among other systems.
Source-capture locker exhaust systems, while currently in use, have room to improve. Better locker design and integration with the building ventilation systems could improve the source capture effectiveness. BAS technology is quickly evolving in ways to improve building IAQ.
Tying the BAS to locally installed ambient air quality sensors or open-source OA quality data to implement real time optimization techniques can prevent intake of OA to a building that is worse than the target IAQ. One possibility is when OA quality sensors pickup wildfire smoke nearby, the BAS could then in real-time engage a smoke mitigation mode to minimize smoke intake to a building. Alternately when in metropolitan areas, a BAS could be tied to various information sources available via the internet that track OA quality and adjust ventilation accordingly.
Creating digital twins is an emerging technology that will revolutionize how buildings are designed and operated. A digital twin is an exact virtual model of a physical building where all the building systems, indoor conditions and outdoor conditions can be manipulated and analyzed for optimal performance throughout the entirety of a building’s life cycle, from design to decommissioning. A digital twin could be used to analyze what the optimal building system design is for the best IAQ. After a building is built, the digital twin could be updated as any given condition changes to help an operator make IAQ related decisions. A digital twin could be used to analyze and make decisions related to just about every aspect of a building with IAQ being only one of them.
Some of these new technologies like disinfecting cabinets require no real integration with other building systems and can even be easily used in existing facilities. Other technology requires more upfront coordination in a building’s design but can be paired with existing strategies to both improve IAQ and save energy.
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