Pursuing this credit means using a high level of air filters at your outside air intakes. To earn this credit, MERV 13 filters must be used at all outside air intakes—no spaces may be omitted. As of November 2010, however, a USGBC addendum removed a requirement for return air circulation to also have MERV 13 filtration.
Buildings where it works…
MERV 13 filters provide higher quality air to occupants and remove pollutants. Mechanical systems typically found in Class-A commercial office buildings are most likely to be compatible with MERV 13 filters. These buildings, which commonly supply outside air through air-handling units or rooftop units, can generally replace existing filters with MERV 13 filters without compatibility issues.
Historically, MERV 13 filters have been more costly than standard filtration media, but the cost premium is dropping as demand increases. MERV 13 filters are now often cost-competitive if not cost-neutral.
…And where there are complications
However, not all mechanical systems are compatible with MERV 13 filters. Incompatibility stems from both a lack of available products that physically fit in filter housings and increased resistance to airflow, known as “pressure drop.”
A MERV 13 filter’s high level of filtration removes more contaminants than traditional media, but also creates more resistance to air moving through it. Because of this, the equipment works harder and uses more energy to move the same volume of air through the filtration system. Some mechanical systems can’t provide the added power required to move the minimum airflow needed. Luckily, newly designed MERV 13 filters that cause minimal pressure drop are increasingly available.
Other mechanical systems, such as packaged, terminal, air-conditioning units (PTACs), are simply not physically compatible with the MERV 13 filters on the market, which don’t fit in the equipment.
Compatibility problems can exist for any type of project but are particularly common in for hospitality and multifamily, because hotel rooms and residential units are often served by small, packaged systems. In most of these cases, MERV 13 filters either don’t fit, or the system can’t overcome the resulting pressure drop.
Minimize the potential energy penalty
The use of higher-level filtration media may also carry an energy penalty—as ventilation fans work harder to move air through the building. This additional energy use may impact your project’s Energy Star rating (as measured for EAp2: Minimum Energy Efficiency Performance, and other credits), as well as the building’s utility bills. However, technological advancements in the air filtration industry have helped manufacturers to lower the resistance to airflow of higher MERV-rated filters and thereby minimize the energy penalty.
You can compare the relative energy impact of filters by checking the filter’s rated “initial resistance to airflow.” Generally, the lower the initial resistance to airflow, the lower the energy use. Information on initial resistance to airflow can be found on product cut sheets.
Consider these questions when approaching this credit
- Is our mechanical system compatible with MERV 13 filters?
- How will the use of MERV 13 filters impact the building’s energy use?
- Is there a cost premium for purchasing MERV 13 filters?