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Can a Furnace Filter Be Too Restrictive?

Visit a big box store and make your way to the furnace filter aisle – there are dozens, sometimes a hundred or more options in front of you. Some filters are made from fiberglass, while others consist of polyester or cotton. There are even reusable filters. All of the different options can cause confusion.

How do you know which furnace filter is right for use with your home’s HVAC system? Filters are not one size fits all – a precise fit is necessary to facilitate proper operation of your heating and cooling equipment. The heating and cooling experts at STAR Heating & Cooling share how to make the right furnace filter selection and why you should never blindly pick a replacement filter.

HVAC Filter Recommendations

Filter Media

There are several types of materials used in HVAC filters. Fiberglass, cotton, and polyester are popular options. The filter media catches contaminants passing through the system in the home’s air supply. A filter with a flat surface is typically made from fiberglass while pleated filters are often polyester or cotton paper.

The technicians at STAR Heating & Cooling recommend pleated HVAC filters. Because of their construction, they do a better job of trapping dust and particles. When the filter material is folded into pleats, the filter has more surface area to capture dust. A flat surface filter has less surface area available to trap contaminants. A flat surface filter can clog in a matter of days depending on how much dust and dirt lurks in your home.

Filter Structure

Another element to consider when shopping for a new HVAC air filter is the filter’s backing. Some filters have wire mesh on the back. The mesh provides structure and helps the filter to maintain its shape. The wire mesh also helps prevent the air filter from collapsing when air circulates through the filter and the HVAC system.

Filter Dimensions

Your old HVAC filter must be replaced with a new air filter of the exact same dimensions. Buying a different size of filter does your HVAC system no favors. If the filter does not fit into the filter chamber properly, it can obstruct airflow and collapse into the unit, causing a blockage. 

Before you shop, check your existing HVAC filter’s dimensions printed on its frame. It will show length, width, and height. 

Filter Efficiency

All furnace filters have a MERV rating which indicates filter efficiency. MERV (Minimum Efficiency Reporting Value) indicates how effective a filter is at removing contaminants of various sizes. For home use, options range from MERV 1 to MERV 13, with MERV 1 being the least efficient option. Filters with lower MERV ratings typically do not last as long and need to be changed more frequently, while higher-rated filters offer longer coverage and better filtration.

There are filters available with MERV ratings above 13 – the scale goes all the way up to 20. Past about MERV 13, a high efficiency filter can cause more harm than good in a residential heating and cooling system. The makeup of these high-efficiency filters can be too restrictive for the unit, creating a barrier to good airflow. The HVAC system may struggle to pass air through the air filter and expend more energy in its attempts. Ultimately, system damage can result from use of such filters at home.

If you have questions about what filter rating is appropriate for use with your HVAC system, ask your HVAC technician for professional guidance. We are here to help you get the perfect fit!

Changing Your Furnace Filter

Furnace filters need to be replaced on a regular basis. How long an air filter lasts depends on several factors, from its size and construction to the air quality conditions in your home and how frequently your heating and cooling system runs. Homeowners should check the air filter monthly to assess its condition and determine if a replacement is warranted.

General guidance on HVAC filter replacement frequency is as follows:

  • Low MERV air filters that are one-inch thick last about a month in most cases.
  • Two-inch filters can be used for one to three months.
  • A three- or four-inch air filter needs replaced every six to nine months.
  • Five- and six-inch filters require replacement every nine months to one year.

Contact Star Heating & Cooling for Your Home’s HVAC Needs

Eliminate the guesswork of shopping for a furnace filter when you purchase replacement air filters from Star Heating & Cooling. Our licensed technicians know the right size furnace filter for every heating and cooling system and help you navigate available options to find the filter that meets your household needs as well as your budget. Contact us today to learn more about how to improve your home’s indoor air quality!