Seasonal Impact on Air Filters in HVAC Systems

Air filters are used in furnaces, air conditioners, and air handlers in residential and commercial buildings. They trap and remove particles in the air, and are necessary for improving airflow and efficiency in HVAC systems. Their function in HVAC also means they’re affected differently in different seasons. As summer comes to an end, now is the best time to inspect your air filters. 

As outside air is pulled into the HVAC unit, filters collect and trap dust, pollen, pet dander, and other airborne contaminates, ensuring the air is cleaner when leaving the unit and entering the indoor environment. Seasons with higher amounts of dust, mold, allergens and pollen, or that overuse air conditioning, will cause filters to become clogged quicker. This is why the end of cooling season is the most important time to inspect and replace your air filters, as the spring and summer months will lead to greater degradation of the filter. There are simple, evident signs that tell if your filter is clogged or dirty: visible dust or dirt-buildup on the filter, discoloration of the filter from white to gray or brown, or reduce airflow from vents. 

Clogged or dirty air filters restrict airflow, reduce cooling efficiency, and increase energy use. In fact, dirty filters can increase energy consumption by up to 15%. In addition, they cause poor air quality, coil freezing, and will make your HVAC system work harder, the strain of which can cause damage to other components, leading to higher repair costs, inefficiencies, or total system shutdown. To make sure you’re keeping energy costs down and air quality up, it’s best to replace your filters after the high-contaminant summer months and ensure your system is ready to take on winter.  

Types of Air Filters and When to Replace Them 

HEPA filters (High-Efficiency Particulate Air) are a type of filter that meet strict standards like capturing 99.97% of particles 0.3 microns in size. While not all filters are HEPA filters, these will most commonly be found in commercial, industrial, or manufacturing facilities with strict air quality requirements. HEPA filters will have a clear HEPA certification on them, so do not be fooled by other filters claiming to be “HEPA-like” or “HEPA-style.” One key differentiator with air filters is their MERV rating. MERV (Minimum Efficiency Reporting Value) is the rating system that determines the filtration efficiency in capturing airborne particles. The ratings range from 1 to 20; the higher the number, the greater the efficiency. MERV 8 through 13 filters are the most common for residential or commercial HVAC use. Only buildings where air quality is of higher importance, such as hospitals, laboratories, cleanrooms, and pharmaceutical manufacturing facilities, are higher MERV ratings necessary. 

Fiberglass Air Filters 

• • Replace every 30 days 
  • MERV 2-3 rating 
  • Smaller surface area can capture large air particles 
  • Cheapest option 
  • Best for low-pollution areas or less powerful systems that will struggle with higher resistance 

Pleated Air Filters 

• • Replace every 60-90 days (depends on usage) 
  • MERV 8-13 rating 
  • Larger surface area can capture smaller air particles 
  • More expensive upfront but longer lifespan makes them cost-effective over time 
  • Best for places with high pollution, dust, allergies, and/or pet dander 

Now that cooling season is over, make sure you’re HVAC system is ready for heating season by inspecting and replacing your air filters! LONG PartsPros stocks a variety of air filters for furnaces, rooftop units, and air handlers, so you can make sure your system has high efficiency and high air quality.