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Energy Efficiency

Not All Air Filters Are Created Equal

Breathe easier by investing in high-quality filters

The air filter in your home’s heating, ventilation and air conditioning system has an important job to do: improve the air quality in your home.

The air inside our homes is full of particles originating from inside and outside sources. This junk-laden air flows through a filter before encountering the HVAC equipment. Without a filter, the cooling coils would get clogged and the heating side would burn off whatever was in the air. Ah, the smell of burnt hair in the morning …

Air filters trap a lot of debris that otherwise would end up back in the house, stuck in ductwork, clogging HVAC equipment—or in our lungs.

But enough with the HVAC and air quality primer. Let’s tackle types of air filters.

There are more filter choices than you can shake a stick at. Fortunately, they can be broken down into two nicely defined categories, making the selection process manageable. The two are:

  • Permanent or disposable
  • Flat or pleated (with a handy MERV rating)

Disposable filters are the most prevalent. Some in the flat group look like they will stop only particles larger than a golf ball. They have flimsy cardboard frames and a thin, flat mesh you easily can see through. They’re cheap, but don’t waste your money. Your HVAC system and lungs deserve better.

Made of stronger, opaque fibers, pleated filters perform better. While they look impervious, air can move through under pressure, leaving airborne cargo trapped as it should be.

Remember MERV? Minimum efficiency reporting value is a rating system that tells you how effective a filter is at trapping particles—a measure of efficiency. The scale runs 1–16 (higher is better) and is based on trapping particles 3–10 microns in diameter. Research shows that residential filters with a MERV rating of 7–13 are likely to be as effective as true high-efficiency particulate air, or HEPA, filters. This class of filter is used in cleanroom manufacturing and, at the extreme end, can trap particles much finer than the diameter of a human hair, as small as 1 micron.

So, should you run out and grab a supply of high-MERV filters? Not without some research. All filters increase resistance to airflow, but higher MERV values come with greater levels of resistance—making the system work harder. A system working too hard loses efficiency and increases wear on operating components. HVAC systems are designed to operate at a particular pressure and all should support MERV ratings of 1–4.

How do you decide which level of filter to use? If you have your system’s operating manual or can find it online, check for recommendations. Otherwise, go with a decent (MERV 3–5) pleated filter, either disposable or permanent, and check it once a month to see how it is performing. Change or clean it whenever it looks dirty. Factors such as pets that shed, the amount of carpeted versus hardwood floors and the presence of cigarette smoke in your home will affect how often filters need to be changed.

Invest a little more and breathe a lot easier with a quality air filter and regular replacement—a simple change that pays big dividends.