Before we discuss the different types of air conditioning and heating filters and which one is the best for you, it needs to be stressed how important it is to keep your air conditioning and heating filters clean. Air flow is very important to the efficiency of your Heating, Ventilation, and Air Conditioning (HVAC) system and filters play a key role in maintaining the proper air flow. Whether it be your A.C. system or your Heating system, both HVAC systems need the proper amount of designed air flow throughout the system. Dirty filters restrict the airflow which results in higher energy and repair costs to you.
There are different definition, categories, and ratings for HVAC filtering media. High Performance HVAC will do its best to take the confusion out of this and help you better understand these different categories and ratings so you may choose for yourself. First of all, HVAC filters are rated by a MERV value. MERV stands for Minimum Efficiency Reporting Value and is a method developed by ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers) to test the effectiveness of HVAC air filters. The higher MERV number the higher the effectiveness of the HVAC furnace filters to block certain particles and compounds. There are three distinct categories for HVAC air filters. These are:
Mechanical Air Filters – This is your typical off-the-shelf throw-away HVAC filter. This filter collects particles in its filtering medium. After it collects so many particles you simply remove it, throw it away, and replace it with another. Note that some mechanical filter media’s are washable. HEPA (High-efficiency particulate air filters) are also in this category. There are three sub-categories for mechanical air filters. These are:
A1 and A2 – these are the standard 1 inch thick filters. These are typically rated MERV 1 to MERV 4.
B filter media’s are 2 to 4 inches thick. These filters typically range from MERV 1 to MERV 12.
C filter media’s represent the HEPA filters. MERV ratings for these filters exceed MERV 13 and are the most expensive.
Electronic Air Cleaners – The electronic air cleaner does not qualify for a MERV rating because its efficiency can change depending on how clean it is. It is important that electronic air cleaners are cleaned on a biannual basis (more frequently in dusty environments) for best performance. Additionally, these work best when used in conjunction with a mechanical filtering media.
Gas Phase Absorption – uses carbon to absorb odors and gases from the air stream. This media is not very effective at removing particulates and is used in mainly laboratory and industrial settings.
It is important to understand that the better the mechanical filter is at filtering the air the faster it will load up (or become clogged with particles). This can affect the performance of your equipment and the frequency of changes. Unless your dwelling is particle and dust-free do not believe that the filter will last for three months despite the filter manufacturers claims. Additionally it is imperative that the filter has the proper fit with no air leaks around the frame which holds the filter.
Now that you understand filters, how they work to eliminate particles from the air, and the different types and ratings for filters, you need to take action to set up a planned filter changing routine. It is recommended that filters at least be checked every 30 days for excessive load up of particles. If the filter is excessively loaded on a thirty day check then you need to narrow the time 3 weeks or relax that schedule if they are not loaded up. Some modern digital thermostats come with a filter reminder feature that will flash based on number of days or run-time of the fan. These thermostats help you remember to change or check your filter on regular intervals.
In closing, remember that filters are very necessary not only to keep particles out of the air inside the dwelling but also to protect the equipment. If you don’t have a filter in the system somewhere or there is a filter that is excessively clogged the HVAC equipment will fail and you will lose your HVAC comfort system until corrective action is taken. Set a schedule and stick to it so that you keep your air clean and the equipment protected.