In 2020, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommended switching from MERV 8 filters to MERV 13+ filters in order to help protect against the COVID-19 virus. For facility managers this has provided a variety of challenges, including considerations around increased pressure drop in HVAC systems due to the more restrictive nature of filters with higher MERV ratings.
What is Pressure Drop in HVAC Systems?
Pressure drop describes what happens when air pressure is decreased from one section in an HVAC system to another section downstream. As air moves through an HVAC system and encounters a filter, the filter creates resistance to the airflow as it removes particles and contaminants from the air. This results in lower air pressure on the side of the filter from which the air exits. The lower air pressure will then cause wasted energy because the HVAC system will need to spend more time and power to heat or cool the building to the desired temperature.
Are MERV 13 Filters Susceptible to Excessive Pressure Drop?
Filters with higher MERV ratings are more restrictive because they are capable of filtering more particles than filters with lower MERV ratings. Since MERV 13 filters (https://www.rpfedder.com/filtration/merv-13-filters/) are on the higher end of the rating scale, they can be susceptible to excessive pressure drop. The wasted energy (and associated energy bill costs) required to push air through a higher MERV-rated filter to overcome the increased pressure drop shocks some owners.
However, an important factor is that MERV ratings are not standard and the quality of a filter will vary from one brand to the next, meaning that pressure drop will vary between different filters that are rated the same. For instance, the most common cause of pressure drop is a dirty filter and some low-quality MERV 13 filters will clog more frequently, leading to increased pressure drop which requires more frequent filter replacements. Additionally, some brands drop their MERV rating almost immediately upon first use (e.g., a so-called MERV-13 becomes a MERV-9 as it’s used – it can’t hold its efficiency).
Consider the following MERV 13 pressure drop chart, comparing a premium MERV 13 filter vs. a lower quality MERV 13 filter. These filters are installed in two air handling units (AHUs) in the Delaware Biotechnology Institute. The chart also provides instructions on how to determine electric fan energy consumed by AHUs in your own facility.
Fan Energy Savings Breakdown
- We cannot assume that the two AHUs operate at the same airflows, so the costs normalized for airflow are best used to make an estimate of annual energy savings by using 5-Star air filters.
- Estimated energy cost reduction from high capacity air filters, normalized for airflow: ($0.463/cfm – $0.575/cfm) / $0.575/cfm = -19.5%
Estimated energy savings from 5-Star filters per AHU, extrapolated to annual basis (assuming 24/7 AHU operation, 34,235 cfm airflow per AHU): ($0.463/cfm – $0.575/cfm) x 34,235 cfm = $3,834 annual electric energy savings per AHU.
Conclusions Drawn from the MERV 13 Pressure Drop Chart
- $3,834 will be saved annually per AHU in reduced fan energy by using 5-Star air filters.
- Additional annual savings of $2,413 are realized via lower change out costs, reduced solid waste, reduced CO2 emissions AND lower purchase price.
How to Mitigate Pressure Drop Caused by MERV 13 Filters
We’ve identified that there is an increase in pressure drop and energy costs when switching to MERV 13 or higher filters. The good news is that institutions and other commercial/industrial facilities can take steps to lower their operating costs by adjusting their air filter strategy, namely by using higher quality or premium filters to save money in the long run. The following example illustrates how this can play out for a hospital investing in higher quality filters to reduce their energy and filter replacement costs.
Need Help Upgrading to MERV 13 or Higher?
If your facility needs to upgrade to MERV 13+, R.P. Fedder can help you. We offer a variety of premium air filters that can help you meet the latest filtration recommendations while keeping energy costs as low as possible. Both Rensa and Camfil make some of the best filters on the market: they are the most energy-efficient, have a longer and more effective service life than other filters, and feature a lower pressure drop than competing brands.
Our filtration specialists can help you determine the right air filter strategy for your facility.