Three different technologies - fabric duct, heat recovery ventilators, and ultraviolet lights - affect indoor air quality (IAQ) in different ways. The following case studies detail the distinct benefits of each technology for their applications in manufacturing facilities, schools, and hospital/health care facilities.

Fabric Duct Proves Versatile, Easy To Install

Cincinnati Air Conditioning is a 70-percent design-build mechanical contractor. Company President Mark Radtke said employees are always on the lookout for technology that "makes us better than the next guy."

In just the last five years, the contractor has become a Metasys dealer for Johnson Controls (Milwaukee) and formed a Thermolinear Division for controlled environmental room construction.

The company has also developed a niche market for fabric duct as an alternative to sheet metal - and that's what Radtke sees as one of the company's up-and-coming growth areas.

In two years, the contractor has used fabric duct on more than a dozen projects. In the next five years, Radtke predicts his company will be involved in more than 100 projects that will use fabric ductwork.

"With every project we bid now, we look into the possibility of using fabric duct," he said. "Obviously, a lot of clients never heard of fabric duct, so it adds to the perception that we're on the cutting edge of HVAC design."

Numerous Benefits
For Cincinnati Air, fabric duct means there is less outsourcing to sheet metal fabricators. This helped Radtke decide to postpone an estimated $2 million investment for its own sheet metal shop - a hefty investment.

Fabric duct also can improve a project's IAQ through more evenly distributed airflow, according to Radtke. "After using fabric duct on several projects, I'm convinced it's much more functional than sheet metal duct with registers," he said.

That doesn't mean he was an easy sell. For several years, he said, he resisted recommendations from friend and manufacturer's representative Jeff Johnson, Virginia Air (Cincinnati), to try products from DuctSox (Dubuque, Iowa). Then some industrial design-build project challenges for The Andrew Jergens Co. (Cincinnati), offered no air distribution feasibility other than fabric duct.

The challenge: retrofitting the HVAC in the cosmetic company's 40,000-square-foot, high-speed packaging area in Jergens' 100-year-old Cincinnati factory, with its 11-foot ceiling clearances. After the initial installation, the ductwork would need to be moved periodically to accommodate heavy machinery reconfigurations. Fabric duct can be easily removed by sections.

Plant management was also concerned with the HVAC system's appearance. Radtke specified a premium model, DuctSox red Sedona, with "Quality & Safety" factory-silk screened in gray letters onto the fabric. The 600 linear feet of 28-inch-diameter duct are double-hung from a two-row cable system that prevents wrinkling in large-diameter duct.

Sedona fabric duct is well-suited for the project's airstream humidity injection used to maintain relative humidity levels critical to packaging quality control, according to DuctSox.

Another reason Jergens retrofitted the HVAC system was the difficulty and cost involved with periodically cleaning the existing metal duct. Now the in-house maintenance staff can disassemble the duct for laundering.

More than 200 linear feet of fabric duct was installed in this Lexus dealership.
More Projects
This project got Radtke thinking about using fabric duct for the Lexus Rivercenter auto dealership across the Cincinnati River in Covington, Ky. The newly constructed, 30,000-square-foot project is turning into a Lexus corporate prototype.

More than 200 linear feet of black Tuftex® (the fabric DuctSox uses) ductwork hangs in roughly 15,000 square feet of open-architecture truss ceiling space in the service, service write-up, and customer pick-up areas. Adding to the streamlined look is Sonic Vent linear diffusion. "Lexus wanted a high-tech, streamlined look, which is what their cars are all about," said Radtke. "Add that to the Lexus logo that was silk screened in gold on the duct about a dozen times throughout the facility and you've got a very dynamic look."

IAQ was an important factor in choosing linear vents. They distribute air conditioning and heating more evenly and gently than metal duct/register systems, stated Radtke.

Another industrial client, Keebler Baking Co., a division of Kellogg, Cincinnati, presented a different reason for using fabric duct. The HVAC retrofit of a 20,000-square-foot cookie production area inside the 200,000-square-foot plant could not afford a production shutdown in its 24-hour/seven-day operations. "Putting up metal duct would have taken weeks to install," said Radtke. "We installed the fabric duct and the suspension system that hangs it all in one Saturday with little interruption to production."

Additionally, Microbe X fabric duct inhibits microbial growth and meets Food & Drug Administration (FDA) regulations. Keebler's in-house maintenance staff plans to annually disassemble the white duct from its cable suspension system and launder it to further maintain plant hygiene. "The FDA requires a metal like aluminum or stainless steel that's easier to clean, so that would have raised the materials price considerably," Radtke said.

The contractor has a lot of fabric duct projects on the drawing board right now, including the Cincinnati Police Historical Museum, a Mazda dealership showroom and service department, a printing plant, and others.

"It's funny that we haven't seen much fabric duct on plan-and-spec work," said Radtke, "but that's due to the conservative nature of the consulting engineer community. It's a shame because their customers are missing the boat. When engineers and contractors both realize that they're losing projects to competition using fabric duct, they'll jump on the bandwagon."

ERV Helps School IAQ And Cuts Energy Costs

There are a number of considerations when you're looking at IAQ in schools. Poor IAQ can lead to a range of problems in students and faculty, from undesirable odors and afternoon drowsiness, to Sick Building Syndrome and increased absenteeism.

Bringing in more outside air is easier said than done, particularly in schools with limited funding - and that's most of them. In many climates, outside air should be preconditioned before it is brought into the building. "Good indoor air quality requires a delicate balance between comfort and efficiency," said HVAC system manufacturer Lennox.

Take the Middle School Seventh/Eighth Grade Center in the Missouri Raymore Peculiar School System, for instance. When they began a remodeling-expansion project in 1999, designers decided areas that contained a higher volume of active students each hour, such as the gymnasium, needed more fresh air to meet fresh air standards from the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

"We needed to decrease the extreme temperatures outside the building to maintain an even climate control and bring more fresh air in for the students," said Joe Coon, Raymore Peculiar School System HVAC service engineer and technician. "The oxygen levels had to increase, but we needed to minimize energy use at the same time."

Air Quality vs. Energy
Coon knew that an energy recovery ventilator (ERV), with the help of an energy recovery wheel, could transfer heat and humidity from the incoming outside air to the exhaust air in summertime, increasing the overall efficiency of the entire system. It would do the opposite in the winter, preheating outside air and adding moisture.

Coon and Jack Woodbury, director of Building Grounds, decided to get the ERV offered on Lennox L Series packaged rooftop units. This particular ERV is a stand-alone make-up air unit that uses an energy recovery wheel as already described.

"An energy recovery wheel serves a similar purpose as air conditioning, only it moves energy out of incoming outside air into outgoing exhaust air," the manufacturer explained. "Instead of using refrigerant or water, a chemical desiccant is used to recycle cooling from the exhaust air into the incoming ventilation air."

As the wheel rotates, it absorbs energy from the incoming outside air into the desiccant, then injecting it into the exhaust airstream. It reduces the temperature and humidity difference between the outside air and the return air while bringing in sufficient outside air to improve IAQ, the company said.

The rooftop unit with ERV "drastically reduces the design load on an air conditioning system and minimizes the tonnage of a rooftop unit by 10 to 40 percent," the manufacturer said. The system cuts installed costs even more by reducing the size of ductwork that is required.

"We have three Lennox L Series with ERVs in the Middle School Seventh/Eighth Grade Center and one in Eagle Glenn Fifth Grade Center and we have been nothing but impressed since installation," stated Woodbury.

Florida Hospital Uses Ultraviolet Lights

Firouz Keikavousi is the mechanical engineer in charge of facilities management for Florida Hospital, an Orlando-based acute-care health system with more than 2,800 beds throughout the state. The facilities needed to figure out some new tactics for cleaning coils.

That necessary system downtime "can compromise humidity and temperature control," he has written, "potentially leading to air quality or comfort problems."

Florida Hospital has been installing high-output ultraviolet C-band (UVC) lights in its air-handling units (AHUs), and found that this has reduced or, in some cases, eliminated coil-cleaning programs, "yielding ongoing energy savings, a reduction in HVAC system maintenance, and the elimination of cleaning chemicals," he said. The lights also offer IAQ and infection control benefits.

Keikavousi said he became interested in UVC in 1998, after seeing a presentation on the technology at an ASHRAE conference. "A new generation of UVC devices promised to offer an improvement over the UV lights that were long ago popular for upper air disinfection in hospitals and other health care environments," he said.

"Output of these devices was reportedly so much higher than conventional UV tubes in cold and moving air," Keikavousi said, "that they could be installed just downstream of a cooling coil to eradicate bacteria, viruses, and mold."

The hospital tested out UVC by installing the lights in one air handler - a 27-year-old, 6,000-cfm unit at the main Orlando campus. A UVC Emitterâ„¢ from Steril-Aire Inc. (Cerritos, Calif.) was specified for this installation, and eventually for others, Keikavousi said.

On that particular air-handling unit, "The coil and drain pan areas had a very visible buildup of mold, and the coil was clogged to approximately 50 percent," Keikavousi said. "Within weeks after the UVC installation, static pressure over the coil decreased from 1.8 inches wg to just 0.7 inch wg." Air velocity over the coil increased from 230 fpm to 520. "Both the coil and drain pan areas looked absolutely clean, with no more visible evidence of mold or organic buildup," he added. The air exiting wet-bulb temperature from the unit decreased, from 57 degrees F (before UVC) to 53 degrees (with UVC).

"We calculated the increase in capacity to be 95,245 Btuh, or approximately 7.9 tons of air conditioning," Keikavousi said. "The total installed cost of the UVC Emitters was less than $2,000. Given the number of our facilities and the number of AHUs in these facilities, we estimate yearly energy savings well into the six figures," not including savings due to reduced maintenance.

That first air handler, he said, "has essentially returned to its original performance specifications and has continued to operate like a ‘new' system since we installed the UVC devices. The coil and drain pan areas have also maintained their clean condition, eliminating the necessity for the monthly inspections and twice-annual cleanings that used to be required."

After reviewing a few more unit test results, the hospital agreed to expand its use of UVC. By the beginning of 2004, more than 100 AHUs in seven Florida Hospital campuses were outfitted with the lights, as well as some ceiling-mounted and portable air recirculating units.

Although the hospital's interest in UVC was primarily a maintenance-driven issue, "We have never lost sight of the fact that infection control is one of the primary functions of this technology," Keikavousi said. "Over the past year, we have incorporated UVC into self-contained ceiling units that are equipped with prefilters, fans, and HEPA filtration."

HEPA filters are able to trap bacteria, he pointed out, but "they are not always effective against smaller microbes such as chicken pox, smallpox, and other highly contagious viruses. UVC energy's ability to inactivate all types of bacteria and viruses, no matter how small, is well documented.

"Though we do not yet have sufficient data to measure the effectiveness of UVC as an infection control tool at our facilities," Keikavousi said, "our infection control people have greeted it as a welcome enhancement to current prevention strategies."

Publication date: 08/16/2004