Replacing a dirty HVAC air filter is one of the most important jobs a Frisco homeowner can perform throughout the year. The air filter has two purposes: First, it helps clean the air in your home, trapping particles that can cause respiratory illnesses down the road and aggravate existing conditions such as allergies, asthma and COPD. Secondly, the air filter protects your HVAC equipment against dust and grime buildup, which can cause serious damage to parts and components.
How to Choose an Air Filter: MERV Ratings
Air filters range in quality from the cheapest flat fiberglass filters to the most expensive pleated filters with higher density. It’s difficult to judge the quality of a filter by looking at it, and that’s where MERV ratings come in. MERV, or Minimum Efficiency Reporting Value, is the most universal standard measure of quality for HVAC filters. The MERV scale for residential systems generally ranges from one to 12, though some homes use filters as high as MERV 16. HEPA (high efficiency particulate air) filters, often used in air-cleaning systems, range from MERV 17-20.
MERV 1 to 4
Flat, cheap and made of fiberglass, filters with a rating of 1 to 4 on the MERV scale are the lowest quality. Because they’re flat, they don’t have as much surface area as the higher-rated pleated filters, which means they’ll need to be replaced more often. Additionally, these low-quality filters only trap about 20 percent of particles larger than 10 microns, such as pollen and dust mites, but allow smaller particles like mold spores, pet dander and dust-mite skins and droppings to pass through and re-circulate throughout the air in your home. It’s best to avoid these air filters, which do very little to improve your indoor air quality.
MERV 5 to 8
Filters with MERV ratings above four are usually pleated, with the folded material providing more area for trapping more particles. Because they have a higher density, they are able to trap between 20 and 70 percent of the particles in your home that are as small as 3 microns, such as mold spores and particulate matter from dusting aids, hair spray and other similar products. MERV 5 to 8 filters are adequate for homes that are pet-free and whose human occupants have healthy respiratory systems.
MERV 9 to 12
The highest-quality filters available for residential HVAC systems are MERV 9 to 12 filters, which trap particles as small as one micron. These particles include some bacteria, as well as lead and humidifier dust. A MERV 12 filter will trap 80 percent of the particles in your home that are between 1 and 3 microns in size, and they’ll trap 90 percent of particles that are between 3 and 10 microns. If anyone in your home suffers from respiratory illnesses or a suppressed immune system, or if your household includes small children or the elderly, choose a MERV 12 filter for the cleanest indoor air. Filters higher than MERV 12 generally will require system modifications in order to work with standard HVAC equipment.
Before you upgrade the air filter, check the specifications of your system to determine the highest quality filter it can accommodate. High-end MERV filters can impede airflow, since they have denser filtration media. When choosing a filter, it’s essential to balance optimum airflow with the best possible air cleaning capabilities.
The Cost of a Dirty Air Filter
A dirty air filter is one of the most common causes for problems with your HVAC system. When the filter is clogged with dust and debris, it can’t trap any more particles. Those untrapped particles infiltrate the system and coat essential components like the fan and motor, often causing their premature failure. Dust buildup on the evaporator coil in the indoor A/C or heat pump unit will interfere with the absorption of heat, and buildup on the furnace’s heat exchanger can cause expensive damage that could require replacing the entire system. Additionally, a dirty filter prevents the optimum flow of air through the system, reducing its efficiency at best and causing it to overheat and shut down at worst. The bottom line is, a dirty filter will cost you money, either through lowered system efficiency or damage to the essential components.
Experts recommend you inspect the air filter every month and, when you see that the filter material is no longer visible, replace it with a clean filter. The old filter slides out of the compartment easily, and the new filter should be inserted with the arrows on the frame pointing toward the main heating or cooling unit, in the direction of the airflow.
For more expert advice about using MERV ratings to choose the right filter for your forced-air HVAC system, please contact us in the Frisco or Allen area at Bill Joplin’s Air Conditioning & Heating.
