Posted on November 19, 2014
For as small as it is, the air filter has a major influence on your home's heating and cooling system. That's especially true around Lufkin and Nacogdoches, considering how much we rely on air conditioning. Choose the right air filter and you'll enjoy reliable, energy-efficient heating and cooling along with better indoor air quality. Choose the wrong model, though, and you could end up damaging the system or, at the very least, failing to improve your air quality.
HVAC Air Filters Come in Several FormsIf you're not familiar with the types of air filters available, you've probably just been replacing dirty filters with the same type month after month. That means you could be missing out on one of the easiest ways to improve air quality and keep the system running efficiently. Understanding the basic filter types that are available to you is the first step to knowing how to choose the right air filter.
- Flat panel filters - This type of filter is made from a flat sheet of fibrous material. Considered the standard air filter, it's the kind your HVAC technician will install if you don't ask for a higher-efficiency model. This disposable filter usually lasts only one or two months.One-inch fiberglass models are the most common among these filters. Their job is to prevent larger pieces of debris, such as hair, carpet fibers and lint from entering the heating and cooling system. While they do this job well enough, they can't stop air contaminants that are small enough for you to inhale, meaning they don't improve air quality in a meaningful way. Flat panel filters made of polyester or other synthetic material are also available. These are more efficient and are capable of improving air quality. If purchase cost is your main concern when looking to choose the right air filter, polyester filters are likely your best bet.
- Pleated filters - The surfaces of these filters are folded into pleats to allow more particle-trapping surface to fit into the same amount of space as a flat filter. Rather than being made of fiberglass, these filters are made of polyester or a blend of synthetic material.One of the greatest benefits of these filters is that they can greatly improve your air quality, and they're easy to install and replace by yourself. If, when you're looking to choose the right air filter for your needs, both efficiency and cost are factors, pleated filters a good option.
- High efficiency particulate air (HEPA) filters - A true HEPA filter can trap 99.97 percent of particles 0.3 microns or larger. You may also find filters labeled "HEPA-like." While these are generally high-efficiency filters, they're still less efficient than true HEPA filters.Although they're marketed as the gold standard among filters, HEPA filters aren't something that can be installed in the average residential system. In order to trap particles so efficiently, these filters are extremely dense. That density causes them to slow down airflow, meaning the fan motor has to work harder to pull air through. In most residential systems, the fan motor isn't powerful enough to operate with a HEPA filter. If you want whole-house HEPA filtration, your HVAC technician may be able to install a HEPA bypass system in your home's ductwork.
Find Your Filter With the MERV SystemMERV is an acronym for minimum efficiency reporting value. A filter's MERV rating indicates its particle-trapping efficiency. The value is based on what percentage of particles in certain size groups the filter can trap. The higher the percentage of smaller-sized particles it can trap, the more efficient it is and the higher its MERV rating. The air filter MERV scale ranges from 1 to 20. A higher MERV indicates a more efficient filter. Once you know what type of filter you're looking for, knowing the MERV range you want will help you choose the right air filter.
- MERV 1 to 4 - Disposable fiberglass filters usually fall into this range. Their filtration ability is so low, the MERV may not be listed on the packaging. Their job is simply to stop larger particles of dust, lint, pollen, and other air contaminants from gumming up the HVAC system. Because they have so little surface on which to hold particles, they need to be changed monthly during the heating and cooling season.
- MERV 5 to 8 - In this range, you'll find the better flat panel filters and, on the higher end, pleated filters. Filters with MERV ratings in this range provide a level of air cleaning that's sufficient for most homes. In fact, filters with MERV ratings between 7 to 13 are nearly as effective as HEPA filters, according research conducted by the US Environmental Protection Agency (EPA).
- MERV 9 to 12 - The filters in these range are either higher-efficiency pleated filters or, less commonly, box or bag filters. Because box and bag filters require a specially designed holder, they're rarely used in residential settings. These filters capture around 95 percent of the dust, pollen, dust mites, and other lung irritant particles in the air.They can also trap certain bacteria, such as legionella. If you have allergies or asthma, choose a filter with a MERV rating of 11 to 12. As a bonus, higher-efficiency filters last longer than less efficient models, so you may be able to use the same filter for as long as six months. That means although they cost more to purchase, you'll end up saving in the long run.
- MERV 13 and above - These are typically box and bag filters not designed for residential use. Filters with MERV ratings above 17 are considered HEPA filters. While choosing the filter with the highest MERV rating might seem logical, it's not a good idea. Filters with MERV ratings above 12 are dense enough to interfere with airflow in some residential HVAC systems. They can place a strain on the fan motor, lowering system efficiency and increasing the chance the motor will fail early.
Making a Final Filter ChoiceOnce you're clear on the types of filters and efficiency levels available, there are a few more things you'll want to consider before you go out and buy a new air filter.
- Clarify your goals - To better choose the right filter for your needs, first get clear on what you want the filter to do. If all you really want is basic protection for your HVAC system, then thin fiberglass filters may be enough. If you'd like somewhat cleaner air, but you're not dealing with a respiratory disorder, consider a filter with a MERV rating around 7 to 9.
- Know your ratings - MERV is handy, but it's not the only rating manufacturers use. Some offer alternatives such as pressure drop, which is also called filter resistance. The higher the pressure drop number, the more the filter interferes with airflow. A higher number generally indicates greater efficiency at trapping contaminant particles, too.
- Check the change schedule - In general, the more efficient the filter, the less often it will need to be changed. How often you'll need to change your air filter also depends on indoor air quality and how often you run the furnace or A/C. Most manufacturers provide guidelines to help you decide how often to put in a clean filter. If you'd rather hassle with your filter as little as possible, pay attention to this information when you choose an air filter.