Modern Solutions Inc.

Do furnace filters really matter that much?
Absolutely! The filters you use in your furnace can make a huge difference in your indoor air quality and the way your furnace works. When you understand what dust is, you begin to understand what a huge difference it can make to the health of building occupants if you use good quality air filters in your furnace and air conditioning system. As a side benefit, your furnace will love you more.

There are actually seven different types of filters used in furnaces. Let’s talk about each of them:

1” Low Efficiency Disposable

These filters are inexpensive but also very inefficient. They allow large amounts of dust particles to pass through them. This can reduce the life of mechanical equipment, allow debris collection on air conditioner evaporator coils which can lead to the growth of mold and bacteria within the system, as well as, allow more dust to be re-circulated into the indoor environment.

1” Low Efficiency Washable

These filters are washable and reusable, but are also very inefficient. They allow large amounts of dust particles to pass through them. This can reduce the life of mechanical equipment, allow debris collection on air conditioner evaporator coils which can lead to the growth of mold and bacteria within the system, as well as, allow more dust to be re-circulated into the indoor environment.

1” Mid Efficiency Pleated Disposable

These filters are more efficient than traditional 1” filters, but are between 3 to 8 times more expensive to use depending on the brand being purchased. However, these are the best option when the use of 1” disposable filters is desired.

2”- 5” High Efficiency Pleated Disposable Cartridge

These filters are very efficient in comparison to traditional disposables, but are more expensive to use than traditional 1” filters and depending upon the model and a person’s ability, may require a service technician to replace them. They have a noteworthy advantage in that they require no monthly maintenance, typically needing replacement only once a year.

4” Washable High Voltage Electronic

These filters are only efficient upon startup. After they collect some dust on the electrically charged panels, they become very inefficient and allow large amounts of dust particles to pass through the system. This can reduce the life of mechanical equipment, allow debris collection on air conditioner evaporator coils which can lead to the growth of mold and bacteria within the system, as well as, allow more dust to be re-circulated into the indoor environment. These filters also require high voltage electrical usage, are subject to zapping noises, and need professional repairs. It is recommended to replace these or disconnect their power supply and retrofit the housing with 1” filters.

1” Washable High Efficiency Limited Life

The filter media becomes electrostatically charged as air passes through it, thereby increasing the particle trapping efficiency over traditional 1” filters. Due to their limited reusable life, these are about equal in cost to use as traditional 1” filters.

1” Washable High Efficiency Life Time Warranted

The filter media becomes electrostatically charged as air passes through it, thereby increasing the particle trapping efficiency about ten fold over traditional 1” filters. Lifetime warranted media makes these the least expensive to use. (This is what I use in my home.)

Notes about filters in general:

Furnace filters should be judged primarily by their efficiency and convenience of use, and not their price. Inefficient filters can cause increased particle passage which can reduce equipment life and efficiency, as well as, causing biological pollution inside the system and a dustier indoor environment.

All furnace filters should be kept clean or replaced for proper operation of ventilating systems. Some require monthly replacement or cleaning and some require annual replacement; follow filter instructions.

Disposable filters should be removed carefully and immediately and very carefully carried outdoors to prevent the dislodging of dust particles indoors. Then placed into a plastic trash bag.

If you have a filter slot opening for the 1” filters on the outside of a natural draft furnace, it should be modified to be no larger than the edge of the filter to prevent negative air pressure near the combustion chamber or an adjacent water heater.

Be sure to install filters according to proper air flow direction. Many people install filters backwards. With some filters, reverse operation diminishes the efficiency and with others it could damage your furnace. Draw an arrow on the air return duct next to the furnace to help you remember the importance of proper placement.

Lastly, if you are using the disposable filters, be sure to take the plastic wrapper off before you install it. I actually found one like this in a home. Can you believe it?

Here’s Mine

This is a picture of the electrostatic air filter I use in my furnace. Electrostatic filters are rinsable or vacuumable. If you get a good one, you’ll never have to buy another furnace filter as long as you live. They come in all sizes and will fit standard furnace filter slots, so there is no need to modify your ducts. There are varying qualities of these electrostatic filters available at the stores and through air purification system dealers. Some are encased in durable metal frames while others are plastic. Also, some have better grades of charged fabric on the inside. A good, reusable filter is an investment, so purchase only the best.

I provide this style of filter at no charge for our air purification system customers.

by Building Inspector and Indoor Air Specialist, Dan Schilling
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