Do Air Filters Matter?

Yes, Yes they do! Not all filters are the same. Not all filters are made for your hvac system. What do I mean? HVAC air filter where never about indoor air quality, it was for protecting the hvac equipment. Matter of fact furnace manufactures designed their equipment to work with the standard fiberglass air filter. Somewhere down the road we started to use filters for indoor air quality, except we didn't tell the HVAC system, which is why in 20 years of testing HVAC system I've only found one that was design correctly with the proper air filter and air flow. That being said, let's dive in deep.

Let's start with airflow and then air filters. (Sorry I'm going to geek out for a minute) Most manufactures of HVAC equipment design system to work on .5 TESP "Total External Static Pressure" this is like blood pressure to you and me, Higher number is bad, lower number is good. Most HVAC duct systems that I've tested in the Midwest Chicagoland have high static pressure numbers (we'll talk about that in another article) so going from a fiberglass air filter to a 1-inch pleated increases the static pressures. Filters have a rating called MERV "Minimum Efficiency Reporting Value" the higher the number, the smaller particulate the filter will collect, but that doesn't tell you how it effects the HVAC system, you know the whole airflow thing. So, let's talk about the different air filters pros and cons.

1. Standard fiberglass air filter: Somewhat protects the hvac equipment. It will catch the large particles like rocks but, not the small dust and allergy issues. fiberglass filters have a MERV-2. Very good for air flow but, does not improve indoor air quality.

2. 1-inch Pleated air filter: There's a wide range of 1-inch pleated air filter starting with a MERV-4 all the way up to MERV-16. Great for catching small particles but, usually rough on static pressure and airflow. Almost all duct systems where never designed for this type of filter.

3. Electrostatic air filter: This kind of filter works on resistant to create electrostatic, that also creates high static pressure reducing the total airflow.

4. Electronic air filter: Works great when new, over time the cells don't come clean and effective value is reduced. Side effect produces Ozone which is not good in occupied buildings.

5. 4-inch Pleated air filter: Have some of the highest MERV ratings around, between MERV-8 to MERV-16. 4-inches gives you the largest surface area collecting smallest particulates with low static pressure drop.

6. Oversized 4-inch pleated air filter: All the same benifits of a standard 4-inch pleated air filter. Greatest reduction in static pressure drops, plus low velocity for better particulate collection.