This Web Exclusive comes from Gina Tsiropoulos, Market Manager, Kimberly-Clark Filtration.
Virtually everyone has been learning to cope with tough economic conditions. For individuals, the loss of jobs and cuts in pay mean tighter budgeting at home: forgoing vacations, dinners out, and luxury purchases. For companies, reduced income and profits often means taking a hard look at line item expenses in an attempt to boost the bottom line.
One line item that may come under scrutiny among facility managers (fms) looking to reduce maintenance expenses is the HVAC system. It may seem perfectly logical, for example, to save hundreds or even thousands of dollars per year in purchasing costs by reducing the frequency of air filter change-outs or by downgrading to a lower-priced filter.
Smart fms should realize the small amount of money saved by reducing or eliminating air filter purchases or by purchasing lower priced (and lower efficiency) filters pales in comparison to the energy and operating costs that can be saved by maintaining a robust air filtration maintenance and upgrade program.
The Role of Air Filtration
Effective air filtration provides the primary defense for building occupants and HVAC equipment against pollutants generated within a building as well as pollutants from air drawn into a building from the HVAC system. It affects the quality of indoor air, which can be two to five times as polluted as outdoor air.
Poor indoor air quality (IAQ) is more than just a nuisance. The cost of poor IAQ to the overall U.S. economy is in the neighborhood of $160 billion in terms of healthcare costs and reduced productivity among workers. Moreover, studies have shown that when indoor environments are improved, businesses can realize up to a 20% improvement in productivity—another strong incentive to pay close attention to enhancing IAQ through proper air filtration.
While air filters play a key role in a building’s IAQ, they also play a major part in the energy consumed to operate the building’s HVAC system. This makes air filtration a wise target for cost reductions as long as the right strategies are followed.
HVAC Expenditures: Myths vs. Facts
There are a number of ways that facilities may try to save money and reduce their HVAC system budgets. For example, facilities may try to delay filter change-outs or upgrades, or they may want to downgrade from high efficiency pleated filters to lower efficiency and lower priced panel filters. These strategies may be short sighted and contrary to cost saving goals; especially when one considers that the U.S. Department of Energy suggests enhancing operating efficiency of HVAC systems can reduce energy bills by up to 20% without significant capital investment.
Myth: Delaying filter maintenance (i.e., change-outs) will help save money.
Fact: While it is true that purchasing fewer filters reduces initial expenses, delaying filter change-outs also causes the filter to run more days at peak energy usage. It doesn’t take long for peak usage cost to offset any savings in the filter price. (See chart below.) That’s because energy use is the largest operating cost involved in air filtration. A filter’s energy consumption accounts for a full 80% of its total life cycle costs. Moreover, the cost of the energy used to operate the filter can be more than eight times the initial purchase price of the filter itself.
It comes down to physics; the energy used to operate filters is directly proportional to the airflow resistance of the filters. The more resistance (due to clogged filters that aren’t changed out as frequently as needed), the more energy is needed to push air through the filter. Resistance typically increases as filters remove more and more contaminants from the air. This filtration is essential for air quality and protection of HVAC equipment, but it comes at an extremely high cost when filter change-outs are delayed.
Delaying filter maintenance not only increases energy consumption, it also increases CO2 emissions; the extra energy consumed by dirty filters drives up energy production and greenhouse gas emissions. According to the U.S. Environmental Information Administration, 1.354 pounds of CO2 are released into the atmosphere for every 1 kWh of electricity produced, making delayed filter maintenance extremely costly to the environment. Plus, because America generates close to 50% of its energy by burning coal, reducing HVAC energy consumption also helps conserve natural resources.
Myth: There is little economic incentive to upgrade a building’s air filtration system.
Fact: Some commercial and institutional buildings in the United States are still using pre-WWII technology in their air filtration system—panel filters. Sometimes called “throw-away” filters, they are constructed in much the same way they were made 75 years ago and are among the lowest priced filters in use today.
For years, it was believed that panel filters provided adequate filtration to keep HVAC systems running cleanly and efficiently. However, a recent study found that panel filters do not provide adequate protection to HVAC equipment, allowing for particle deposits to build on fans and heating/cooling coils, a problem known as “fouling.” Fouling greatly reduces airflow through the HVAC system and prevents heat transfer in the coils, all of which can add up to a significant increase in energy costs. Fouling also leads to expensive and time consuming fan and coil cleaning.
Myth: Air filtration is not in the budget.
Fact: One of the biggest traps that commercial facilities fall into regarding budgeting for air filtration is the NIMB (Not in My Budget) factor. In many cases, one department (and budget) is responsible for purchasing air filters and filter service contracts while another is responsible for energy expenditures. The problem inherent in this system is that the filter purchaser can easily and quite innocently make a costly decision for the enterprise by choosing to buy filters without considering the energy consumption and system operating implications described above.
Reducing HVAC-Related Costs
It is important to remember that filters will only support good IAQ and perform as specified when they are maintained correctly. There are three important factors for proper air filter maintenance and reduced operating and energy costs: following the proper filter change-out frequency and installation steps; upgrading from panel filters to pleated filters; and choosing a filter with a lower resistance to airflow.
Proper filter maintenance is crucial to keeping HVAC ductwork clean. If dirt accumulates in the ductwork and if the relative humidity reaches the dewpoint so condensation occurs, then it can become a breeding ground for bacteria and mold.
For all of these reasons and more, it is important to establish the appropriate filter change-out frequency. However, filters should be changed immediately if they become wet, if microbial growth on the filter media is visible, or when the filters collapse or become damaged to the extent that air bypasses the media.
It is crucial to pay close attention to filter installation during change-outs. The goal is to avoid bypass air (air that does not go through the filter) which occurs when filter media is not properly sealed in the filter frame, when filters are not properly installed and gasketed in filter racks, or when air handler doors and ducts are not properly sealed. Bypass air can cause contamination in housings, coils, fans, and ducts and can increase system operating costs; fouled heat exchangers have diminished heat transfer performance and increased pressure drop, leading to increased energy use and decreased heating and cooling performance. Bypass air can also decrease a filter’s performance and negatively affect IAQ.
Keep in mind that bypass air tends to have a larger effect on high performance filters. A 1mm gap causes a MERV 15 filter to perform as a MERV 14 filter, while a 10mm gap causes a MERV 15 filter to perform as a MERV 8 filter.
One way to lessen the frequency of and purchase costs related to filter change-outs is to choose a high-capacity pleated filter which typically has an extended filter life along with a low resistance to airflow Pleated filters certainly offer advantages over “throw-away” panel filters.
First, while panel filters typically yield performance only in the MERV 1 to 4 range, pleated filters are available with performance up to MERV 13, allowing improved efficiency in capturing both large and small particles. Second, upgrading from panel filters to pleated filters provides cost savings advantages, thanks to decreased routine maintenance and energy costs. Because panel filters allow HVAC system components to become dirty, operating efficiency decreases and energy costs to operate the inefficient system can increase. The small amount of money saved by purchasing a lower priced panel filter can be substantially offset by even a slight reduction in the operating efficiency of the system.
One of the easiest ways to realize HVAC related energy costs savings is to switch to a filter with a lower resistance to airflow. When filters have a lower resistance to airflow, the HVAC system motor needs to overcome less resistance to deliver the required air flow, thus reducing the motor’s energy consumption.
Airflow resistance is calculated with a pressure gauge, which indicates Water Gauge (WG), the measure of the pressure required to lift a 4C-degree column of water a certain distance in the air. For example, a 0.05” WG reduction in a filter’s initial pressure drop (also known as airflow resistance) can reduce energy costs by up to 3.5% or about $7 per filter, while a 0.20” WG reduction in a filter’s initial pressure drop can reduce energy costs by up to 10% or about $28 per filter. While an energy cost savings of $28 per year may not sound like a lot, those cost savings are per filter, not for an entire HVAC system.
Skimping on air filtration during a tough economy has the potential to put facilities even deeper in financial trouble. It can negatively impact IAQ which can increase costs relating to worker health and productivity. It can also increase HVAC system operating and energy costs. While reducing the frequency of filter change-outs or downgrading to a lower-priced (and lower performance) filter may seem like good ways to reduce expenditures, they are not true cost-savings strategies. Because energy costs are the largest component of an air filter’s total life cycle cost, it is imperative for facilities to look beyond the line item purchase price of filters when seeking to reduce their overall costs and instead look at the initial and sustained pressure drops of different filters.