Design with IAQ in Mind
Healthy buildings are of interest to facility owners and managers
Poor IAQ is a major concern for both American citizens and the U.S. economy, because it can impact the health, comfort, and productivity of building occupants. Inadequate ventilation, chemical contamination, microbial contamination, and other common IAQ problems can contribute to an unhealthy indoor environment. That is why many building owners and managers are proactively incorporating IAQ equipment, such as dehumidifiers, energy recovery units, and UV technology, into their facilities.
Indoor swimming pools are notorious IAQ challenges because of chloramines. Chlorine molecules attach to body contaminants, such as urine and ammonia, to create chloramines, which are heavy gases that reside just above the water surface where swimmers breathe. Consequently, inhalers are commonplace at swim meets throughout North America. At the 2007 U.S. Swimming Championships in Indianapolis, for example, USA Today reported several pedigreed swimmers had substandard performances due to IAQ.
Forest Hills Public Schools Community and Aquatic Center, in Forest Hills, Michigan, never had those types of IAQ problems; however, James B. Harrison, associate lead project engineer at GMB Architecture + Engineering in Holland, Michigan, met the potential for chloramines head-on during the facility’s recent HVAC retrofit. Harrison designed an 84-foot-long concrete swimmer bench with a perforated metal face plenum that draws chloramines off the pool surface while also functioning as a return air device. Chloramines-laden air is transported via an underground concrete tunnel duct leading to a new mechanical room’s 30-ton dehumidifier manufactured by Seresco USA. The dehumidifier recovers heat from the return air before exhausting indoor air contaminates.
Prior to the retrofit, spectators were uncomfortable with the same temperatures supplied by one dehumidifier to swimmers in the 12,000-square-foot natatorium. Harrison improved IAQ in the 300-seat, 2,400-square-foot spectator area with the specification of a second dedicated dehumidifier. The 8-ton dehumidifier uses its own newly installed return and supply duct system to maintain the spectator area at 76°F and 50 percent relative humidity while the swimming area dehumidifier delivers a 50 percent rH, 84° space temperature, and 82° water heating via heat recovery.
“The difference in air comfort and air quality for the spectators as well as the swimmers after the retrofit has been incredible,” said Kelly Swieter, aquatic supervisor, Forest Hills Public Schools, who monitors space and water temperatures, rH, and general IAQ daily through his WebSentry smartphone app.
High humidity and warm temperatures in Houston can wreak havoc on air handlers and cause organic matter to quickly clog coils and buildup in drain pans. That is why one of the largest hospitals in the area is systematically retrofitting its air handlers with UV technology in order to keep the equipment clean and prevent IAQ issues.
“It’s humid here, so IAQ problems can be a real challenge,” said Nathan Wittman, director of sales and marketing, Filter Technology Co., Houston, a manufacturer’s representative of numerous HVAC products, including air filters and UV lights. “UV technology makes sense here because it is very effective at keeping coils clean, eliminating organic growth inside the air handlers, lowering static pressure, and improving IAQ.”
Wittman is working with the hospital to gradually retrofit its 450-plus air handlers with UV technology. “We are retrofitting about 20-25 units a year with UV technology from Fresh-Aire UV,” he said. “Standard UV systems are used for the outdoor air system while Fresh-Aire UV’s APCO Rack system is used in recirculating systems. In addition to keeping the coils clean, the APCO Rack system eliminates VOCs [volatile organic compounds] from the air.”
The UV systems fit easily into the facility’s existing air handlers, which has allowed the facility to easily incorporate the technology. The UV systems have also drastically reduced preventive maintenance efforts because coil cleaning is not required as often.
“When you clean an air handler, it stays clean and sanitized for a moment in time but as soon as you turn it back on, it starts to get dirty,” said Wittman. “UV technology works 24/7 and maintains that level of cleanliness around the clock.”
UV technology is proven to eliminate microbial growth and reduce static pressure on the dirtiest of coils. “In one facility we worked in, the coils were plugged with organic growth, and static pressure was upwards of 2 inches. We put in UV lights and within three months we got that pressure down to about 0.75,” said Wittman. “That is what initially gave us confidence in the technology. It’s fine to hear it from manufacturers, but when you see it work so effectively in real life, that makes a big difference.”
Cooling a building in the Arizona desert can be a challenge, especially when the facility has a variety of thermal and IAQ requirements. At the U.S. Arid-Land Agricultural Research Center in Maricopa, Arizona, engineers designed a cooling system for nine buildings totaling 98,000 square feet that contained spaces ranging from greenhouses to laboratories to office spaces. In addition to efficient cooling, HVAC requirements included precise temperature control and high IAQ to service the laboratory space.
“We had specific requirements to meet that were based on government guidelines,” said Russ Mulholland, design engineer, The SmithGroup, Phoenix. “They included part-load operating efficiencies, energy recovery units, quiet operation, and high IAQ.” With that in mind, Mulholland and his team specified equipment from Daikin Applied that included Vision indoor air handlers, Skyline outdoor air handlers, and air-cooled screw compressor chillers.
Four Daikin Vision indoor air handlers with energy recovery coils help to recover as much as 75 percent of the sensible heat energy from the exhaust air stream and transfer it to the supply air stream. Standard recirculating air conditioners, such as fan coils, deliver the conditioned air to individual spaces via ducted forced air. “We pull in 100 percent fresh air at 115°F ambient,” said Mulholland. “The energy recovery coils are a great help because we can recover some of that conditioned air before exhausting it.”
IAQ and energy efficiency are also achieved through standard features in the air handlers that include insulated double-wall construction with a smooth inner liner and gasketed frame channel, a double-sloped drain pan, high-efficiency filters, and optimal performing fans. Because of the strict requirements for laboratories and greenhouses, some areas are evaporatively cooled and others have individual systems tied into the central chilled water system. An additional six Skyline outdoor air handlers help circulate air to the greenhouses.
The research center incorporates a variety of additional energy-saving and IAQ features, as well, including daylighting, glazing and thermal break frames, occupancy sensors, and automatic daylight controls. Its efficient HVAC system includes direct digital controllers, variable frequency drives (VFDs), and energy recovery devices.
DATA CENTER CONTROL
In addition to providing healthy air for occupants, many companies need to invest in clean air for costly computer equipment. That is especially the case in data centers, which often house hundreds or even thousands of servers that must be kept free from particulate-laden air. When Southland Industries was recently tasked with constructing such a data center, the project’s design engineers knew exactly how to accomplish that goal.
The new confidential facility in Maryland included a 150,000-square-foot, 10-MW data center as well as an adjacent 100,000-square-foot office building. There were also numerous support rooms that housed switchgear, transformers, uninterruptible power supplies (UPS), and batteries. The design engineers needed to find a way to keep these areas and the data center positively pressurized so that dirty air would not be drawn into the spaces.
“This can usually be accomplished with some kind of a variable air volume (VAV) terminal, but we needed something with a wider range of flow, tighter tolerance, and reliable feedback,” said Mike Kilkeary, senior design engineer, Southland Industries. To that end, 40 air measuring stations with high-performance control dampers (AMS050) from Ruskin were specified to provide set point monitoring and adjustment.
The AMS050 units were preferred over traditional VAV boxes because the load of the data center and support rooms could vary widely from almost no load to a sudden large load, said Kilkeary. “We needed something that could control a very wide range of set points, and a traditional VAV box cannot provide that kind of flexibility.”
In addition, the project involved multiple control systems, so selecting equipment that could be easily integrated into those systems was essential.
“This was a large coordination effort,” said Jessica Baker, senior design engineer, Southland Industries. “Even though the dampers on the Ruskin units only interface with one of the control systems, the two control systems had to talk to each other, and the equipment had to respond across the two control systems with tight tolerances. Everything had to be integrated, and that was possible to do with the Ruskin units. In the end, it all worked very well.”
Publication date: 12/26/2016