The best furnace filters to use in your home are the ones that provide the results that you want. When trying to choose a filter to use it is important to consider what you objectives are. Just because a filter is the most efficient doesn’t make it the best furnace filter. It just makes it the best choice for a person who has allergies or other health concerns. There are many variables to consider when selecting a replacement air filter for your furnace or air conditioner. We have created a list of the most common types of filters used by home owners. These are not the only furnace filters available but they are among the most common types.

Pleated furnace filters

• Pleated air filters are the most common filters used in residential and commercial HVAC equipment. They are probably the easiest to find at your local hardware store although better pricing is available online.
• These filters are available in a wide range of efficiencies from about MERV 5 to MERV 12. The higher the MERV rating is the more efficient the filter is. This also means that it may need to be changed more often because the more dust it collects the faster it begins to have a negative impact on air flow.
• These filters are very easy to maintain. Simply change them every two to four months or when recommended by the manufacturer.
• One of the things that make them so common and popular is that they are available in custom sizes.

Electrostatic furnace filters

• Some electrostatic furnace filters are very high quality and will last for many years. Wash them once a month and they are as good as new.
• Electrostatic air filers cost more to purchase but they eliminate the monthly expense of buying disposable filters. Pay $50 to $100 up front for an electrostatic air filter or $5 to $10 or more each time you change your disposable air filter. This adds up to decent savings over a 10 year period. If you replace a $5 filter 4 times a year it adds up to $200 dollars in 10 years. A $10 disposable air filter will cost $400 in 10 years. It’s the little things that save you money.
• If you don’t like doing maintenance tasks then these filters are not for you. They must be maintained properly so they will remain effective.
• If Green living and the environment are important to you these filters are a good choice because they reduce landfill usage and they last for many years.

Media air filters (Pre-Cut Media Pads)

• Pre Cut media air filter pads are not used as often as the types listed above because they are not as popular with retail stores.
• If maintenance is not your thing and you sometimes forget to change your filters these may be for you. Media pads are much more forgiving. They have a much greater dust loading capacity than the other filters listed here. This means that when neglected it takes longer for it to negatively impact air flow and you can potentially avoid the decline in equipment operating efficiency that the other filters create when neglected.
• Carbon media pad inserts can be installed with these filters to help control odors.
• Pre cut pads are less expensive than most of the quality pleated air filters.

HEPA filters

• Hepa air filters are the most efficient air filters available.
• These filters utilize the pleated design of standard pleated air filters. The difference is in the number of pleats per inch of filter and the material used in the construction of the filters is much more efficient at stopping dust, pet dander, pollen and other airborne allergy causing contaminants that you may find in your house.
• Some brands, such as the Hepa-Pure, can be cleaned and used several times.
• True HEPA filters are 99.97% efficient and can remove particles as small a .3 microns in size.

Question: I have a Honeywell electronic furnace filter on my furnace. The power panel failed and the unit is very expensive to replace. However, I can install pleated air filters in place of the original electronic cells. The filter size is 20 X 25 X 4 inches thick. As a temporary measure, I have installed 3-1 inch thick MERV 8 air filters in parallel into the filter opening.  How does the MERV rating change when the filters are placed in parallel? Is what I have done a good solution? If not, what would you recommend that I do?

I would remove two of those 1 inch pleated air filters ASAP. Installing filters in this way has a very negative effect on air flow and reduces equipment efficiency greatly. Take a look at your air handler to see if there is a place to install a 1″ filter. Most air handlers come equipped with this filter rack.

Take a look at the pictures on this page “where is my furnace filter” if you are not sure where to look. If you can’t find a place to install a 1″ filter, you can get a 20 X25 X4 MERV 12 filter at NordicPure for a very reasonable price.

Compare Filtrete and Nordic Pure pleated air filters

Question: I would like to save costs by getting a washable air filter, but it seems that none of them can get a MERV over 8, and I’d like something with a MREV of 11 or higher since we have allregies in the family.  How does Boair or air-care-filters.com filters compare to the filtrete ultra allergen. If I need to get a disposable, is the Nordic the best priced disposable filter?

You are correct about washable filters. Although they don’t have MERV ratings they perform close to a MERV 8. Although washable filters have their own positive characteristics, if allergies are a concern for you I would recommend high efficiency pleated air filters.

I did some quick investigating and this is what I found when comparing these pleated air filters

- Filtrete Ultra Allergen filters are $13.88 at Walmart and they have a MERV rating of 11 (I used Walmart because they usually have good prices)

- Nordic Pure Box of 6 is $48.97 which works out to $8.16 each and they have a MERV rating of 12

Both of these pleated air filters enhance the performance of their filters electrostaticly.

Nordic Pure and Filtrete filters don’t support the growth of bacteria, fungi, mildew or mold.

Nordic Pure filters have a higher MERV rating and they are much less expensive than Filtrete Ultra Allergen filters.

Question: I have a Water Furnace and currently use a pleated filter with a MERV 5 rating.  how high can I go before I start restricting the flow too much and damage the system?

A Merv 5 filter is really not very efficient.  If you have a properly sized duct system and you change your air filter regularly I see no reason not to use an air filter with as high as a Merv 12 rating.  as Merv ratings increase so does restriction to air flow, so you always have to be careful.  The reason I mention a properly sized duct system is because if the duct system is undersized it will restrict air flow dramatically and is a common problem in many homes.  A very efficient air filter and an undersized duct system are not a good combination.

There are a couple of signs that may indicate an undersized duct system:

-  The air conditioner coil ices up when the filter becomes dirty.  Most systems will do this if the filter becomes extremely dirty but you should not have this problem if the filter becomes only moderately dirty and you change it regularly.

- Whistling sounds coming from around the air handler access panels can be an indication of an undersized duct system.  This can also indicate poorly fitting access panels.

- If your furnace trips of on the high limit switch, this could indicate an undersized duct system.

There are other things that could cause the problems listed above but they are also signs of restricted air flow.

If you have your equipment serviced regularly ask your contractor if the duct is sized properly.  Opinions vary among contractors regarding filters with high Merv ratings.  Your other option is to try a higher Merv rating and monitor equipment operation closely.

Question: What is the MERV Rating of the BoAir 5-Stage electrostatic filter?

The BoAir 5-Stage electrostatic filter like all electrostatic air filters doesn’t have a MERV rating. MERV ratings are only used to rate media types of air filters such as pleated filters and Hepa filters. But if you compare the Arrestance rating of the BoAir 5-Stage electrostatic filter, which is over 95%, the media type filters with similar Arrestance ratings it is equivalent to a Merv 6 or a Merv 8 filter.

A furnace filter with a Merv 8 rating is suitable for use in you air conditioning or heating system if you don’t suffer from allergies but if you require more efficient filtration to manage your allergies I would recommend a Merv 10 to 12 pleated filter.