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What AC filter should I buy?

AC Air Filters – Clearing Up the Confusion

What kind of air filter should you use? There's a lot of confusion about air filtration and even people in the AC industry struggle with it.  Homeowners will ask me often, “Do you know what we should we do about filtration?”. They may have family members who have allergies or asthma and they're trying to improve indoor air quality, so it's a question that comes up a lot.

One of the most important things to know is that the “high-dollar expensive filters” that you find in home-improvement stores are really not helping you. They are dense, which may make you think they are better, but they are very restrictive to air flow, which is a no-no for a healthy AC system. To get the performance, efficiency, and longevity out of your AC equipment, it has to be able to breathe freely.

If we look at a typical 1-inch filter that most people have, there's not a lot of surface area to this and when you buy an expensive one the material that it's made of becomes more and more restrictive. The idea is that it filters out everything down to the particle level of a virus, however if you're filtering the smallest particles out, down to viruses, then that fine-weave material is going to make it harder for air molecules to pass through as well, and you may not be able to get enough air through that filter to serve the needs of your central heating and air-conditioning system. So the system and the equipment is designed to have a certain amount of airflow and if it doesn't get the airflow that it needs, you're not going to get the performance or the efficiency that the system is capable of delivering. It's a little bit like drinking a milkshake through a straw or the other analogy I use is trying to run around the block with your hand over your mouth. Try that and see how it works. If you do, you’ll know how your poor AC equipment feels when you come home all excited about the new “high efficiency” filter you a lot on.

When we put these really expensive very restrictive filters in our homes, we are effectively starving our central system of the airflow needed for the system to perform and run efficiently. And most returns air systems are too small, to begin with, so the restrictive filter makes an already bad situation worse.

What should somebody do if your system can only accommodate a one-inch filter? We recommend the homeowners to put in a less restrictive filter.

Filters are rated in what's called Merv, and the most restrictive filter is going to be a higher number, like 11 or 13, and your typical blue fiberglass filter might be a Merv 3 or 4. Pleated filters like this might range from Merv 6 up to Merv 12 or 13.

If you can use only a one-inch filter, we would recommend you use a pleated filter but use a Merv 6 filter and change the filter regularly. That's going to let the system get more air and it'll still filter better than just a fiberglass filter.

What a lot of people don't realize is that the filter on the system isn't there for indoor air quality. It's primarily there to protect the equipment and so if you think about the indoor coil that gets cold and wet and if you've got dirt going through the system that's going to be collecting on that wet evaporator coil. Over time that's going to build up a whole layer of dust and dirt and it will stop working properly.

The first thing you want is a filter that can protect the equipment, secondarily if you can also help the indoor air quality that's a good thing. The best thing you can do for filtration air filtration I feel is getting what we call a media filter. A media filter is similar to the one-inch filter but as you can see here, this one is thick, They're typically four to four to five inches thick and the filter media is accordioned in here and so if I was to take this filter apart, the filter media would be twenty to thirty feet of surface area. Even though it's in this small package here the amount of surface area is much much bigger than a one-inch filter and what that gives you is is the surface area allows more air to flow through and far more air than the one-inch filter.

Media filters are the best combination in terms of allowing air flow that your system needs to perform and deliver the efficiency it's capable of and being able to filter particles from the air in your home.

A lot of new homes are equipped with a system that accepts media filters. Media filters are recommended by the Austin Energy Green Builder Program. The other benefit of media filters is that they tend to last six months to a year vs. the one-inch filter that has to be changed every month.

A lot of times, if you have a one-inch filter now, and you have a vertical system that's in a closet when we replace the system we can put a media filter cabinet underneath the unit. There's usually enough room for that. In cases where there isn't room to do that which happens sometimes, we can put this in the return, up under the unit, behind the return grill so it sits up in there. If the unit is in the attic typically there is plenty of room to add a filter cabinet.

We highly recommend media filters to most of our customers because they're not electronic, they are not a super expensive thing and they really do work well.

Give us a call (512) 280-0011.