HVAC Trends: Filtering Out The Rest
By Brian Kraemer
From the January 2005 issue of Today's Facility Manager magazine
The HVAC field constantly has to evolve in order to meet the needs of today's facility manager. HVAC is one of the most important elements in maintaining a productive work area. Often times, the results of an effective system are not seen by employees, but they are felt. Ranging from temperature controls to particles in the air, HVAC systems bear a substantial load in keeping an office productive and its occupants happy.
A good system is unobtrusive. It runs quietly and consistently, keeping the air clean and the temperature constant. However, even the best systems can use a nip here and a tuck there. But the advances in the industry are more than cosmetic. New directions in filter technology improve air quality and affect energy costs; meanwhile, advances that happen out of sight should not be put out of mind.
Clean Air, Low Costs
Perhaps the most important task of the HVAC filtration system is keeping the air stream particle free, but it is not the filter's only function. According to Dave Matela, a certified air filtration specialist for Kimberly-Clark, based in Neeah, WI, there are 70,000 visible and invisible particles in one quart of air. The average human breathes about 16,000 quarts of air every day, and it is critical for a facility manager to make sure employees are breathing the right sort of particles.
Keeping the air of a facility clean begins with the HVAC system itself. "The needs of a facility manager will determine exactly what sort of filter should be purchased," says Matela. "A low efficiency filter will keep dust and lint from clogging the heating and cooling coils of an HVAC system, whereas medium or high efficiency filters are typically used to remove bacteria, pollen, soot, and other small particulates."
Once a facility manager has considered what the filtration needs of the building are, there is another economic factor to consider-pressure drop. Pressure drop is the resistance to air flow created by filter media, and the lower it is, the higher the energy savings. "The lower you can take the pressure drop down," says Matela, "the more energy savings there will be across the industry." Selecting a quality filter with a low pressure drop will equate to energy savings which will save the facility money in the long term.
The Synthetic Age
Manufacturers of filter media are all aiming for the same goal: to increase efficiency and lower pressure drop. According to Matela, the goal is to create a better product. "We want to move up the filter efficiency chain by taking a specific media and taking the drop down to provide higher energy savings."
Filter efficiency is judged in two ways. Initial efficiency refers to the performance of the filter out of the box, while sustained efficiency is considered over the filter's lifetime. The difference is simple. Filters with a high sustained efficiency but lower initial efficiency will not perform as well out of the box because it needs time to collect dust and get dirty. An initial high efficiency filter operates at a certain level of efficiency once it is installed.
One movement to increase efficiency, in both initial and sustained performance, is to change the material from which the media is made. Matela says, "synthetic media can be manufactured from a polypropylene, polyethylene bicomponent made using spunbond or melt blown technology which provides low pressure drop, high initial efficiency, and sustained efficiency over time." These advances contribute to better IAQ and lower energy costs.
The effects of these new technologies, Matela continues, have shown a change in the type of filter used over time. "If you look historically, pleated filters have moved from fiberglass and cotton/polyester type materials to synthetics. Fiberglass or cotton/polyester media used to be the lion's share of the market, but now synthetics have come in and it has evened out."
Filtering More Than Air
Once air passes through a filter media, the onus of heating or cooling a building is passed to the duct work. The ducts transport the clean air through the building and distribute it to desks and offices. But facility managers have to consider not only the quality of the air when it arrives, but how it gets there.
In addition to wanting clean air, employees have stressed their preference for quiet air. One remedy is to line the ducts with insulation. "If you've ever been sitting in a conference room and the air conditioning kicks on so you can't hear the speaker at the front of the room, you'd know it's important to line ducts." says Renee Chesler, director mechanical installation business, at Valley Forge, PA-based CertainTeed Corporation. Loud systems distract employees, creating a challenging work environment.
Mixing The Weave
Duct liners were mainly composed of either textile or rotary fibers. "A rotary fiber is a shorter hair fiber that isn't as strong, and it has a tendency to break apart easily, especially at the machine shop. But because it is a shorter fiber, it has historically been able to get better acoustical value and thermal resistance," says Andrew Goldberg, mechanical product manager for CertainTeed.
However, with advancements in technology, a movement away from strictly traditional lining has begun, because new products are beginning to catch up with the old. One indicator is R-value. This is a rating that shows how well duct insulation resists conducting heat and noise. "Textile products weren't able to achieve rotary type R-values or acoustical values because of the nature of the fiber: you get a better acoustical resistance when you use a rotary," says Goldberg.
With the introduction of a new textile-rotary fiberglass liner, the market has become more competitive. "With the new blend," continues Goldberg, "we're often able to equal rotary noise reduction coefficient values or get them so close that the difference is negligible." The new liner is composed of mostly textile fibers which are bonded together with a thermosetting resin which prevents loose fibers from entering the air stream. "The liner is encapsulated, if you will, providing high r-values and also high noise reduction coefficient values," Goldberg concludes.
The Bottom Line
As technology moves forward, there is often the mentality that the newer something is, the smaller and less expensive it should become. And since it is the latest piece of technology, it should do the job better and more efficiently than the previous version.
But sometimes, Chesler says, the only way to increase efficiency and savings is to spend money in the beginning. "It's great if you can build a building for $40 or $50 million, but if you can spend a few dollars more making sure that the building is thermally and acoustically efficient, then the building will provide years of service and yield years of savings."
This highlights another point that Chesler makes. Not only will lining a duct reduce noise in the office, but it will also provide thermal resistance, decreasing the amount of air that escapes, and in turn, lowering costs.
As the emphasis on a comfortable work environment rises, facility managers have become even more involved in the everyday life of employees. By taking simple preventive steps, the office can remain an easy place to work. But a comfortable workplace does not necessarily mean a wasteful workplace.
A gracious facility manager may want to keep the buildings internal air particle free. Advances in synthetic filter media technology raise IAQ and also contribute a lower pressure drop, which will keep employees happy with the air. Superior air quality coupled with a quiet HVAC system will create a distraction free work environment that employees can thrive in. And the facility manager who orchestrated it all will be pleased with worker happiness, but more so with the money saved on energy costs.
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