4 Types of Air Filters: Which Do You Choose?


How do you choose an air filter?

If you’re like many homeowners, you simply go to the hardware store and pick whichever filter fits your return air duct. But while this method saves you time in the store, it may not save you money or improve your health; ill-fitting, overly restrictive, or inefficient filters can run up your energy bill and produce poor air quality in your home. With a little education, you can make more discriminating choices.

Before you choose an air filter, you need to learn about Minimum Efficiency Reporting Value (MERV) ratings. MERV ratings tell you the effectiveness of your air filter. They are measures of the number of particles a filter can trap as compared to the total number of particles it’s trying to filter. That may sound complicated, but it just means that if you put two air filters in the same room, the one that traps fewer particles has a lower MERV rating than the other.

It seems like knowing MERV ratings would make a filter simple to choose, right? After all, higher efficiency seems preferable to lower efficiency. But there’s a catch. It may sound like a contradiction, but high efficiency air filters can sometimes make your HVAC system less efficient by blocking too much air flow across the heat exchanger. This means that the system can’t heat or cool enough air to control the temperature correctly in your house. Your energy bills could increase, and you could risk damage to your furnace due to overheating.

The best filter for your home is one that removes the most pollutants from the air while allowing your HVAC to perform at peak condition. Older HVAC systems or those with leaky ducts may need filters with lower MERV ratings. It could take you some experimenting to find out which filter works best for you. Luckily, most of your choices are relatively inexpensive.

Fiberglass filters

Fiberglass filters are one of the most popular kinds. They’re often blue; you’ve probably seen them in hardware stores. These thin, flat panel surfaces are composed of a dense fabric of glass fibers, most of which run perpendicular to airflow. They tend to have the lowest MERV ratings, often between 1 and 4.

While fiberglass filters do an excellent job of protecting your HVAC unit from large dust particles, they’re not the best filters to use if you have allergies. They will not trap mold, pollen, or other smaller particulate irritants.

Pleated filters

Pleated filters comprise folded sheets of cotton or polyester-blend fabric. They are folded accordion-style, so that more fabric surface can fit into a smaller area. The more pleats, the more easily air can pass through this filter. That’s a good thing, because this kind of filter is often high-efficiency, and older HVAC systems can be overtaxed by trying to pull air through it.

If you find a polyester filter with lots of pleats and a MERV value of 6 or greater, it can be an ideal air filter solution that removes many pollutants from your home while keeping your HVAC system in top working condition.

Disposable electrostatic filters

Electrostatic filters usually have MERV values of 10 or greater, so they’re very effective at de-contaminating the air inside a home. They contain multiple layers of polyester blend materials, framed by a polyester mesh. These filters create their own static charge! As air passes through positively-charged outer material, particulate matter becomes charged, as well. It is then attracted to the negatively-charged inner material. That’s how electrostatic filters trap all kinds of particles, including mold and pollen. Smokers or residents with allergies or asthma may be attracted to this kind of filter. However, electrostatic filters can be on the pricey side.

Washable electrostatic filters

These filters are similar to their disposable brethren, but are usually framed in aluminum, cased in aluminum mesh, and made of washable material. They’re incredibly cost-effective; their average price is around $20, and you only have to replace them every 3-5 years. To maximize their effectiveness you need to wash these filters every three months or so.

There is some debate as to whether washable filters actually live up to the hype. They can have MERV ratings of 10 or greater; on the other hand, they aren’t always high efficiency, and it’s sometimes difficult to tell the difference. If they’re not fully dry when you replace them in your air exchange, they can grow mold and bacteria that is then circulated throughout your home. If you choose a washable filter, be sure to check its MERV rating, clean it regularly, and dry it thoroughly.

If you still have questions about the type of air filter that’s best for your home, call Newcomb and Company. We’re happy to talk to you about your HVAC system and your air quality needs.

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