Increased awareness of Indoor Air Quality (IAQ) and the pollutants and particles that are in the air have changed the idea of what "good" air filtration is. The health effects of breathing air with a high amount of small sub-micron Particulate Matter (PM) have been proven to be detrimental, and building occupants are demanding better filtration for their workspaces, schools for their children, and even in industrial and manufacturing areas. An entire new industry has even popped up for portable and wearable devices monitor air quality and PM in real-time at relatively low cost.
Because of this interest in higher efficiency filters, like the MERV 11 air filter, they have exploded in populartiy and it is rare new design specifications don't have high efficiency filters in the plans. Manufacturers have responded to this increased demand by developing a wide array of options for the MERV 11 air filter because it costs more than traditional filters and each manufacturer wants to differentiate themselves and gain an advantage and more revenue with the specific design that they feel best suits them. To cut through all the marketing speak (or B.S. as we call it) we have created this quick overview of the options available that removes brand names as we represent over a dozen different lines and focus just on the filter design.
A Quick Note on Filter Media: Air filter media (the part that actually filters pollutants from the air) has two major groupings Coarse-Fiber/Synthetic and Fine-Fiber. It has been proven through a multitude of studies that air filters using Coarse-fiber/Synthetic media lose their ability to capture particles as they load and therefore what starts as a MERV 11 air filter drops in efficiency once it starts capturing particles. ASHRAE, on page 3 of their 52.2 test manual, acknowledges this downside of coarse-fiber synthetic media.
These filters are avalable as 1", 2" and 4" deep making them a common replacement for lower efficiency panel and pleated fitlers. However, that ease of conversion comes at a price - these filters typically have a shorter lifespan than their lower-efficiency counterparts and all of them use coarse-fiber synthetic media. Which means you are only getting a temporarily higher removal effciency of small sub micron particulate.
Older style high effeicncy filters are these box style ones that have a metal casing and are 6" or 12" deep. These have largely been replaced by other more modern styles of filters as they are expensive, difficult to handle, bulky, and typically don't last very long. There are still some rare situations where these filters do outperform other styles, but as technology and filter design advances the box style filter is certainly on the outside looking in.
Here is a filter style that is on the rise. Available now in depths of 2, 4, 6, and even 12 inches it is a versatile filter and a favorite among OEMs for it's sapce saving design. However, many of these filters do use coarse-fiber synthetic media so you run into a temporary vs full-time particle removal issue. Also with the compact design you again usually suffer short filter life and higher energy use. There are not really any applications where we suggest this style of filter, but unfortunately many new HVAC systems are being designed in a way that limit your options and you get stuck with this really mediocre filter style. To make sure you can keep your options open and take advantage of new technology and styles as they get developed make sure the filter section can accomodate a minimum of 15" deep filter with a periphial header, or just use a universal air filter housing.
No other style of filter has more variation in build-quality from manufacturer to manufacturer than Bag filters. Using an assortment of coarse-fiber synthetic, fine-fiber, and blended medias, a multitude of pocket depths, numerous pocket counts, and various pocket shapes it is very difficult to compare one bag against another. This is best represented by the cost of these bags as a "24x24x12 MERV-11 Bag filter" by that specification alone can range in price from $10-$95 each. Clearly there are quality differences between these, but that low price is enticing and is making the bag style filter rise in popularity as more and more low-bid contracts are awarded.
This is the newest of styles for high efficiency air filters, and again have a wide range of design options including:
- coarse-fiber synthetic or fine-fiber media
- 2-V, 3-V, and 4-V panel configurations
- Straight or Radial V layout
- Single Header or Box
The V-Bed style filter is a good all-around option and does a good job of mixing product life and cost, while also being one of the lowest energy users - making it a favorite of sustainability professionals.
Conclusion: With so much selection a MERV 11 air filter has it is best to contact an air filtration expert to evaluate your specific needs, equipment, run-time, application, and environmental conditions. All of these things should impact your selction to maximize filter life and performance; anyone offering a one-size-fits-all solution probably doesn't have your best interests in mind and is looking to just make a quick sale and fill your filter banks with what is most adventageous for them. When it comes to high efficiency filtration a thorough assement goes a long way.