Frequently asked questions

What is the MERV rating?
How does my filter choice effect my energy savings?
What is the important of life-cycle costs?
How can life-cycle cost be applied to energy efficiency?
Why is filtration important in schools?

What is the MERV rating?
A typical MERV rating tells a specifier the arrestance rating of the filter at three particle sizes of 0.3-10 microns at a certain face velocity. For example, a rating of MERV 10 at 0.93 indicates a filter with a MERV 10 arrestance when operated at an airflow of 0.93 cubic meters per second, which is a little less than 500 feet per minute, or 2,000 cubic feet per minute (cfm) for a standard 2-foot-square filter. The required MERV rating for filters will follow directly from the maximum allowable particle concentrations in the three bands of 0.3-1.0 microns, 1.0-3.0 microns and 3.0-10.0 microns.

A rating of MERV 10 corresponds to 50-65 percent efficiency for particles 1-3 microns and above 85 percent efficiency for particles 3-10 microns.

A rating of MERV 13 corresponds to less than 75 percent arrestance efficiency for particles 0.3-1 microns, above 90 percent efficiency for particles 1-3 microns, and above 90 percent efficiency for particles 3-10 microns.

A rating of MERV 15 corresponds to 85-95 percent arrestance efficiency for particles 0.3-1.0 microns, above 90 percent efficiency for particles 1-3 microns, and above 90 percent efficiency for particles 3-10 microns.

Although the standard only lists arrestance efficiencies for MERV values to 16, continuously higher ratings can be easily added. In fact, the table lists ratings up to MERV 20. Ratings of MERV 16 to MERV 20 correspond to HEPA and ULPA filters.

How does my filter choice effect my energy savings?
According to the U.S. Department of Energy, our nation’s K-12 schools spend $6 billion on energy, while colleges and universities spend close to $2 billion each year. Healthcare facilities also spend a staggering amount on energy — $5.3 billion annually.

In many cases, older buildings, with their aging mechanical systems, are to blame for energy inefficiencies. In fact, a significant portion of energy costs for educational and healthcare facilities can be tied to space heating and cooling, thanks in part to HVAC systems that are not optimized for energy conservation.

Improving an HVAC system’s energy efficiency does not have to be costly, however. For example, simply upgrading the HVAC air filtration system can help to reduce energy costs while also improving indoor air quality (IAQ) – an issue of increasing importance in terms of its effect on academic performance.

Many filter suppliers consider the media used in the filters as a commodity, resulting in the filter’s price being the determining selection factor. It’s important to understand, though, that the cost of energy used by filters far outweighs the initial price of the filter itself. In fact, energy costs can be 10 times the initial filter price for a standard pleated filter and 4-5 times the initial filter cost for higher efficiency final filters.

What is the important of life-cycle costs?
The best way to use filters as an energy conservation tool is to consider the total life-cycle cost of the filter and the filter’s long-term effect on energy costs. The three major components of life-cycle cost for HVAC filters are: initial price and maintenance, energy consumption and disposal. On average, energy cost accounts for an astounding 81 percent of the total life-cycle cost of a filter system.

How can life-cycle cost be applied to energy efficiency?
The key issue is the filter’s pressure drop, as measured by two filter test standards from the American Society of Heating, Refrigeration and Air-Conditioning Engineers

(ASHRAE): ASHRAE 52.1-1992 and ASHRAE 52.2-2007

Development of new materials has given the filter industry a chance to produce lower pressure-drop media while maintaining high particle capture efficiencies, thereby providing the ability to reduce electricity costs and improve IAQ simultaneously.

Switching to a lower pressure drop filter is one of the easiest changes for facility managers to make in an effort to reduce energy costs. That’s because, with a lower pressure drop filter, the HVAC system motor needs to overcome less resistance to deliver the required air flow, thus reducing the motor’s energy consumption.

Once you’ve decided to upgrade your HVAC filter media to a lower pressure drop filter in an effort to reduce energy costs, it’s time to swap out the old filters for new ones. To extend the life-cycle of the filter, and reduce life-cycle costs, rely on the manufacturer’s suggested change-out frequency, or monitor the pressure drop of the filter and

change the filter when it achieves its recommended final pressure drop.

Why is filtration important in schools?
The American Public Health Association states, “…every child and school employee should have the right to an environmentally safe and healthy school that is clean and in good repair.”

While we know many of the problems of school indoor air quality problems can be solved with good engineering practice and proper Maintenance, Operation, and Repair (MOR), cleaner air provided by increased levels of air filtration provide the solution upon which many of the IAQ problems develop.

“When the buildings air filters do not remove the particles from the air the occupant’s lungs become the filter.”
-H.E. “Barney” Burroughs-building Wellness Consultants