Everyone has been learning to cope with the tough economy. For some companies, reduced income and profits means looking at facility expenses, such as the building’s HVAC system. For example, facility managers may look to save purchasing costs by reducing air filter change outs, or by downgrading to a lower-priced filter.

However, the small amount of money saved by reducing or eliminating air filter purchases or by purchasing lower-priced, 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.

AIR FILTRATION PLAYS A ROLE

Effective air filtration defends building occupants and HVAC equipment against airborne pollutants inside a building.

Poor IAQ is more than a nuisance. In fact, the cost of poor IAQ to the U.S. economy is around $160 billion, in terms of health care costs and reduced worker productivity. Moreover, studies have shown that when indoor environments are improved, businesses can improve productivity up to 20 percent - another incentive to enhance IAQ through proper air filtration.

While air filters play a role in a building’s IAQ, they also play a role in the energy consumed to operate the HVAC system. This makes air filtration a good target for cost reductions.

OVERCOMING CUSTOMER OBJECTIONS

To save money, facilities may try to delay filter change outs or upgrades. Or they may downgrade from high-efficiency pleated filters to lower-efficiency and lower-priced panel filters.

These strategies may be shortsighted, especially considering that enhancing the operating efficiency of HVAC systems can reduce energy bills up to 20 percent without significant capital investment. Owners unfortunately often feel that delaying filter change outs will save money. However, while purchasing fewer filters reduces initial expenses, delaying filter change outs causes the filter to run at peak energy usage. It doesn’t take long for peak usage cost to offset savings in the filter price. This is because energy consumption accounts for 80 percent of a filter’s lifecycle costs, and can be more than eight times the purchase price of the filter.

The energy used to operate filters is directly proportional to the filter’s airflow resistance. The more resistance - due to clogged filters that aren’t changed out when needed - the more energy is required to push air through the filter. Resistance typically increases as filters remove more contaminants from the air. This filtration is essential for IAQ and protecting HVAC equipment, but it comes at a high cost when filter change outs are delayed (Figure 1).

Owners often argue that air filtration is not in their budget. This is one trap that commercial facilities seem to fall into more regularly. One department and budget may be responsible for purchasing air filters and filter service contracts while another is responsible for energy expenditures. Consequently, the filter purchaser can make a costly decision by choosing filters without considering their energy consumption and operating cost implications.

REDUCING HVAC COSTS

There are two important factors for air filter maintenance and reduced operating and energy costs: following the proper filter change-out frequency and installation steps, and choosing a filter with a lower airflow resistance.

While it is important to establish the appropriate filter change-out frequency, filters should be changed immediately if they become wet, if microbial growth on the filter media is visible, or if the filters become damaged so that air bypasses the media.

Pay close attention to filter installation during change outs. The goal is to avoid bypass air, 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 sealed. Bypass air can cause contamination in housings, coils, fans, and ducts and can increase HVAC 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 filter performance and negatively affect IAQ.

Bypass air tends to have a larger effect on high-performance filters. A 1-millimeter (mm) gap causes a MERV 15 filter to perform as a MERV 14 filter, while a 10 mm gap causes a MERV 15 filter to perform as a MERV 8 filter.

One way to lessen the customer’s purchase costs related to filter change outs is to recommend a high-capacity pleated filter, which typically has an extended filter life and a low airflow resistance.

One of the easiest ways to reduce HVAC-related energy costs is to switch to a filter with a lower airflow resistance. When filters have a lower airflow resistance, the HVAC system motor needs to overcome less resistance to deliver the required airflow, thus reducing the motor’s energy consumption.

For example, a 0.05-in. water gauge (wg) reduction in a filter’s initial pressure drop can reduce energy costs by up to 3.5 percent or about $7 per filter, while a 0.20-inch wg reduction in a filter’s initial pressure drop can reduce energy costs by up to 10 percent or about $28 per filter. These cost savings are per filter, not for an entire HVAC system.

CONCLUSION

Skimping on air filtration has the potential to put facilities deeper in financial trouble. It can negatively impact IAQ, which can increase worker health and productivity costs. It can also increase HVAC system operating and energy costs.

Because energy costs are the largest component of an air filter’s total lifecycle cost, it is imperative to look beyond the purchase price of filters and instead look at the initial and sustained pressure drops of different filters. To help your customers compare operating and energy costs of various filters, consider using a cost-savings calculator.

Publication date: 11/16/2009