ASHRAE Standard 62.1 specifies minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects.
The 2013 edition revised and improved the standard in several ways, including two important upgraded air filtration requirements:
- The filter requirement on air entering wetted cooling coils has been modified to change the MERV rating from 6 to 8.
- Air filters with a MERV of 11 or higher are now required when the building is located in an area where the national standard or guideline for PM2.5 is exceeded.
The new MERV 8 requirement on air entering wetted cooling coils is important for several reasons:
- By reducing the particulates passing through the filter, it reduces the potential for particulate deposition on the coils that could lead to microbial growth or other contamination of the HVAC system.
- It also provides for a 20-35 percent increase in capture efficiency for E3 particles – from 35-50 percent under MERV 6, to greater than 70 percent under MERV 8, meaning twice as many E3 particles are captured before they can become deposited and support microbial growth.
The new requirement for MERV 11 filters in areas exceeding PM2.5 guidelines is also important because MERV 11 filters are able to filter more than 65 percent of E2 particles, which makes a big difference in protecting the health of building occupants.
“This is a clear shift in the industry away from the lower MERV ratings associated with panel filters and toward higher efficiencies available with pleated filters,” explains Robert Martin, Associate Category Manager, Kimberly-Clark Professional Filtration. “Pleated filters using electret-treated media will let buildings meet these higher efficiency rating requirements.”
Martin says that it is crucial to pay attention to the energy implications of switching to a higher MERV filter, noting that energy consumption will depend on what type of filter people select.
“Increases in energy consumption will be more dramatic for buildings that use mechanical filters,” he says. “For those who use filters with electret-treated media, there will be less of an impact since the treating allows the media to filter particles without creating as much airflow resistance.”