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Air Filters

Spending More For Air Filters Is Not Necessary


In order for your home’s central heat or cooling system(s) to work properly, they must have some form of air filtration. Most homes in the metro Charlotte area have face grills on a wall, with tabs or screws that give access to the filter. Others may have a filter on the furnace or air handler which is located in the crawl space.

The air filter serves two purposes:

  • 1) to keep dust and dirt from being recycled into the air you breathe and
  • 2) to keep the blower motor and wheel clean.

So, let’s consider the first purpose – keeping clean the air you breathe. You can probably guess that the replacement air filter business is huge, perhaps a multi-billion dollar per year cash cow; just walk into any Costco, Home Depot, Wal-Mart or grocery store and voilà.

Given all the options of filters, you might think that the more you spend on a high efficiency filter, the cleaner your air is going to be and the longer that filter can remain in use. However, with regard to wall and ceiling air filters (the ones behind grills), NASCAIR recommends and prefers the basic pleated filter which is replaced every 30 days. The cost will be around $3-4 per filter. Here’s our reasoning, but first a question — do you have dogs, cats, children, doors opening and closing frequently, colds, allergies, pollen, cooking, aerosols and dirty clothes in your home? If you do, why would you keep a filter, with all the gathered germs, dirt and dander, sitting in your system’s air flow for three months? Whatever is on that filter is growing (bacteria) and will stop airflow.

“Aren’t more expensive air filters better, don’t they remove more dirt?” The answer is yes, and no. The more expensive filters do have a higher particulate removal value but they also get stopped up easier, causing the blower motor to work harder and creating a higher energy bill.

Many older homes and some of the more expensive homes have the filter located in the crawl space on the “return” side of the duct work. These filters are called “media filters” – large filters in large cabinets. The advantage to a media filter is that it can last up to a year before being changed, the key phrase being “up to a year”. These filters last so long because their pleating is typically 4-5 inches deep and thus has lots of surface area to share in the collection of dirt. We don’t like the idea of leaving a filter in place for a year (same reasoning as above); don’t leave it any longer than 6 months.

NASCAIR Heating and Cooling does not recommend using the woven, mesh looking, really cheap air filters; they collapse easy and all it keeps out is farm animals, small children and Tonka toys.

A final thought: when people move into a new home or ask us for advice on filters and duct cleaning, we suggest that they open the air return in the hallway or ceiling and, using a flash light, inspect the filter and return duct work. If there is dust and dirt, the ducts and returns should be professionally cleaned.

Once you have the peace-of-mind that your filter and duct work are clean, then you can plan a systematic change out of filters every 30 days (and gauge for yourself if this is the correct timing). Vacuum often, brush dogs outside, keep linens clean, don’t use air fresheners or aerosols and change the filter every 30 or so days — these will make a big difference in your indoor air quality here in the metro Charlotte area.