Making the Grade With Improved Air Filtration

Located in Framingham, MA, the Joseph P. Keefe Technical School serves about 800 students, with a curriculum that combines academics and vocational education. Housed in a 30-year-old facility with approximately 300,000 sq. ft. of space, the school offers programs in automotive technology, carpentry, cosmetology, electrical, plumbing, metalworking, culinary arts and various other trades.

The school’s commitment to education does not end with its students; even its custodial and maintenance staff receives ongoing training and education. For example, the school’s Facility Director Ken Whidden recently arranged for instruction, training and testing on the latest technology required to maintain the school’s heating, ventilation and air conditioning (HVAC) air filtration systems. For this, Whidden turned to programs such as HVAC Air Filtration Choices for Today, the U.S. EPA’s Tools for Schools programs and the National Air Filtration Association’s (NAFA) Certified Technician (NCT) program.

“HVAC and IAQ training for maintenance personnel ensures that day-to-day IAQ is maintained to the highest standards possible,” Whidden notes.“The NAFA Certified Technician program provides the school with qualified personnel with the skills necessary to properly maintain the HVAC air filtration system in our school.”

Improving HVAC System Cleanliness

As part of The Keefe Technical School’s ongoing facility maintenance efforts, the school recently made a significant investment in having its HVAC ductwork and coils cleaned. After the cleaning, they looked for ways to keep those HVAC system components clean — both to maintain acceptable indoor air quality (IAQ) and to reduce maintenance costs. Keefe turned to air filtration experts for help.

“Some of the classrooms utilized special air filtration and air cleaning systems,” says Stephen Nicholas, NAFA Certified Air Filter Specialist (CAFS), president of Air Industries.“Activated carbon filtration in the cooking classroom and dust-removing air cleaners in the woodworking classroom are two examples. However, the building’s overall air filtration system needed to be upgraded.”

The first issue was the disposable, two- in. fiberglass panel filters used in a one-stage filtration system on some of the school’s 42 air handlers. These “boulder-catchers” had a Minimum Efficiency Reporting Value (MERV) of 1-4, which meant they did not do a good job protecting the coils and associated ductwork and were not capable of contributing to good indoor air quality for the students, faculty and staff.

Nicholas also noticed that eight-in.-deep, extended-surface, cartridge-type air filters specified by the original equipment manufacturer (OEM) were used in most of the building’s other air handlers. These were MERV 5-6, which meant they were only removing between 35 and 49.9 percent of particles in the three- to 10-micron size range, based on ASHRAE Standard 52.2-1999.

In addition to the relatively poor filtration efficiency of the original air filters, the gasket material on the filter holding frames and air handler doors was deteriorated or, in many cases, missing completely, thus allowing air to bypass the filters, which further contributed to poor IAQ issues. Moreover, servicing these cartridge filters was difficult and time-consuming. Technicians spent about five minutes per filter on change-outs because they had to undo a complicated cage-and-clip system.

“The original filters were difficult to put into the filter housing, which used a gasket-and-clip system from the 1970s,” Nicholas says. “So, because the original air filters were so difficult to maintain, they ended up being neglected.”

The result? The air filtration system was being compromised, allowing the heating and cooling coils to become loaded with dust. This not only caused higher system operating costs, but also allowed dirt from the coils to get into the drip pan, where it could clog and cause standing water in the pan, which could potentially become a mold issue.

According to Nicholas, improving IAQ and reducing maintenance costs and service time would go hand-in-hand with keeping the HVAC system components hygienically clean and would allow the school to exceed the MERV 6 filter efficiency required by ASHRAE Standard 62.1 “Ventilation for Acceptable Indoor Air Quality” under section 5.9 Particulate Matter.

High-Efficiency Air Filtration

Whidden, Nicholas and lead HVAC Technician Tim Rivers, NCT, and their staff evaluated several air filter products against the following criteria:

• filtration efficiency/MERV,

• documentation and test reports,

• construction quality,

• initial cost versus life-cycle operating cost and

• labor and installation considerations.

For the air handlers with a two-in. track, Keefe upgraded from the MERV 1-4 fiberglass panel filters to two-in.-deep MERV 11 high-capacity pleated filters.

For the air handlers using the MERV 5-6 cartridge filter, Keefe chose to upgrade to a four- in.-deep, high-capacity MERV 11 extended surface pleated air filter. According to ASHRAE Standard 52.2-1999, the MERV 11 filters would effectively remove 65 to 79.9 percent of one- to three-micron size particles and more than 85 percent of particles in the three- to 10-micron size range.

The new MERV 11 pleated filters were able to be installed in the existing filter frames. New filter holding clips/latches were added to the frames, to replace the missing and non-functional old clips and to ensure a positive seal for the filter. Closed-cell neoprene gasket material was installed on the filter holding frames and doors of the air handling equipment to help provide an airtight seal, which forces air to go through the filters, thus avoiding air bypass.

Reduced Maintenance

With the new MERV 11 pleated air filters, technicians can remove and install the filters in about 15 seconds each, instead of the four to five minutes it took previously, since the new filters do not have the same number of complicated elements. This gives the school’s maintenance staff more time to address other duties.

Nicholas, Rivers and their staff installed Magnehelic pressure gauges on all of the air handling units so that technicians could effectively monitor and manage air filter change-outs by air flow pressure drop. Previously, the school used inclined tube manometers to read air filter pressure drop. With the magnehelic gauges, there is no gauge fluid to purchase and refill. Instead, a simple set screw is adjusted to zero the gauge after each filter change-out. Instead of a filter life of about one to two months, the school now gets three to four months of useful service life out of each filter.

“Typically, increasing filtration efficiency results in higher pressure drops, which may increase operating and energy costs,” Nicholas says. “But with the extended surface MERV 11 pleated filters we chose, you get higher filtration efficiency with a very minimal increase in pressure drop.”

The new four-in.-deep MERV 11 filters have about the same amount of filter media (26.1 sq. ft.) as the original eight-in.-deep MERV 5-6 filters (29 sq. ft.). The initial clean filter static pressure at 400 to 450 FPM (feet per minute) is 0.21 in. water gauge (w.g.), which is 0.06 in. w.g. higher than the 0.15 in. in w.g. static pressure of the old MERV 5-6 cartridge filters. The increase in filtration efficiency far outweighs the slight increase in the initial pressure drop, making this a good value proposition. Additionally, the money saved in labor and installation more than offsets the additional cost associated with the slightly higher initial pressure drop.

“Without any system retrofits or modifications to the blowers, we have saved on both labor — reducing change-out time and frequency — and associated disposal costs since upgrading to the MERV 11 pleated air filters,” Whidden says. “The higher efficiency filters also keep the HVAC ductwork clean while allowing the heating and cooling coils to operate at peak energy efficiency. Plus, the improvements in particle capture efficiency achieved by using higher efficiency filters and by ensuring proper seals is huge and contributes to the overall indoor air quality of the school.”


While reducing maintenance costs and time is a positive result of the air filtration upgrade, Whidden and Nicholas say that the more satisfying result is seeing reduced absenteeism among students and faculty thanks to the improvement in indoor air quality.

“The administration of J.P. Keefe Technical School is committed to clean air and the health of our students and staff,” says Whidden. “Good IAQ is a major contributor to an environmentally safe and healthy school that is clean and in good repair.”

“We’re in the process of quantifying the real benefits of IAQ improvements,” Whidden concludes. “I encourage other schools to upgrade their air filtration systems so they can provide a safe, clean and comfortable indoor environment for their faculty and students as well. Once you evaluate the life-cycle costs of the filter upgrade, along with the labor savings, the cost of the upgrade itself is minor.”

Sponsored by the National Air Filtration Association (NAFA), the NAFA Clean Air Award recognizes facilities, companies and organizations for using effective air filtration in maintaining a clean and healthy environment.