HVAC Filter FAQs


Virtually every HVAC system has some sort of filter, most of which should be replaced on a regular basis to keep your air conditioner and/or furnace running efficiently. Filters are typically made of tightly woven fiberglass, paper or cloth over some kind of framework, creating a semipermeable barrier that traps harmful particles from passing through. 

HVAC filters are meant to improve the quality of the air I breathe, right?

Actually, the primary job of an HVAC system filter is to protect the inner mechanisms of your air conditioning equipment from being damaged by dust and particulates (although, improving indoor air quality is a valuable side benefit). However, a lot of the particles in your home or building never get close enough to the intake of your HVAC to go through the system and get filtered out. Plus, the air is only actively being filtered while the system is running—and the vast majority of systems don’t run 24/7, even during the hottest and coldest seasons. If you are sensitive to particulates in the air, consider getting a standing air filter for heavy traffic areas in your home rather than counting on your HVAC to be your only source of filtration.

Are furnace filters and air conditioner filters the same?

Generally, yes. If your home or building has a central heating and air-conditioning system or HVAC, it will use the same type of filter regardless of whether you are heating or cooling. If you have separate systems, the filter will function exactly the same, but each system may use different sized filters.

How important is changing the filter?

Very. When your air filter is clogged with dust or particles, the system has to work much harder to pull air through, which can lead to:

  • an overheated furnace
  • higher utility bills
  • colder temperatures while the heat is on
  • damage to your HVAC system
  • poor air quality
  • mold spores inside your system, which are then distributed through the home
  • and more!

How often should I replace the filter?

Most manufacturers recommend replacement every three to six months, but during high-use seasons, it’s a good idea to get into the habit of visually checking your filter more often. If it starts to look clogged, go ahead and replace it.

What’s the deal with reusable filters?

Most people are familiar with disposable filters, which typically come with a cardboard frame. These are not designed to reuse and must be thrown away. But long-term reusable filters do exist, and although they are typically pricier up front, they can save you money in the long run, as long as you are willing to take care of them. Reusable filters should be hand-washed once every month (while your system is turned off) and allowed to dry completely before being reinserted, in order to avoid the development of mildew or mold. While reusable filters may require more work, they can last for years and help keep additional trash out of landfills.