HVAC Filters

Minimum Efficiency Reporting Value (MERV) is used to measure the effectiveness of air filters on a scale of 1 to 16. The higher the MERV rating, the greater the filtration, i.e. the smaller the particles it can catch. The Centers for Disease Control and Prevention (CDC) recommends to improve central air filtration to the MERV-13 level (or the highest compatible with the filter rack) and to seal edges of the filter to limit bypass.

However, updating an HVAC system’s air filters may not be as simple as it sounds. For instance, a common factor that will get overlooked is that most HVAC systems that were designed for lower MERV filters (likely most of them) will need to be rebalanced for the new filters. The higher the MERV rating, the better the filtration but also the higher the static pressure (or resistance) that the fan must work against, resulting in a drop in airflow. The reduced airflow could cause comfort problems and even frozen coils. To prevent these issues, the airflow will need to be measured with the new filters installed, and then the fan speed will need to be increased to achieve the designed airflow.

Yet this is still not a “one size fits all” solution for all. Many HVAC units cannot handle the higher-rated filters. Using a filter with a higher MERV rating may cause the motor to burn out. This is why it is important you have a trained technician review your unit before making any changes.

Other Building Ventilation Recommendations

In addition to replacing filters, ASHRAE recommends the following actions, with the ultimate goal being consistent and frequent air changes:

1. Increase outdoor air ventilation (use caution in highly polluted areas); with a lower population in the building, this increases the effective ventilation per person.
2. Open minimum outdoor air dampers, as high as 100 percent, thus eliminating recirculation. (During mild weather, thermal comfort or humidity within a facility normally wouldn’t be affected. During extreme weather, this clearly becomes more difficult to control.)
3. Consider portable room air cleaners with HEPA filters.
4. Consider ultraviolet germicidal irradiation (UVGI), protecting occupants from radiation, which is particularly in high-risk spaces such as waiting rooms, prisons, and shelters.

Developing Solutions

While the experts are recommending the above items, they are not mandatory across the country. States’ policies vary. Not to mention that COVID-19 research is still developing.

The result, in the near term, is likely to be a patchwork — some commercial buildings, schools, colleges, and other facilities will make investments, while others will not. One example of an organization making the investment to fight COVID-19 is KIPP DC, a publicly funded and privately operated network of seven school campuses with 1,200 employees and 7,000 students. KIPP DC has taken huge measures, working to find the ideal system optimized to filter the coronavirus.

Want more HVAC industry news and information? Join The NEWS on Facebook, Twitter, and LinkedIn today!