Furnace filters were added to furnaces by the manufacturers to protect the blower and the heat exchangers from being fouled by contaminants in the air. Filter manufacturers differentiated their products by using various filter materials that removed more contaminants from the air, but at the expense of restricting the airflow.
What type of filter should you be using on your furnace? There is not one filter that fits all needs. You want to remove air contaminants so that the inhabitants of the house are breathing healthy air, but an overly restrictive air filter can slow the rate of airflow placing a bigger load on the furnace fan causing the motor to fail more quickly. It can also cause the furnace heat exchanger to over-heat and eventually fail.
Filters are rated as to their Minimum Efficiency Reporting Value (MERV). This value is from 1 to 16. A value of 1 means that it lets the maximum amount of air through. It does this by filtering the larger particles and letting the smaller particles through. It filters most of the particles that foul the blower and the furnace and air conditioner heat exchangers. Because it lets the smaller particles pass through it is not the best choice for people with allergies and respiratory problems.
Filters with MERV values between 8 and 12 are best for people with allergies and respiratory problems. Because they filter so many more particles, they clog more quickly and must be changed more often, usually once a month. A clogged filter will put a bigger load on the blower, which will shorten its life. It will also cause the furnace to run hotter which will shorten its life.
There are three types of filters you should select from depending on your needs.
Fiberglass air filters
Fiberglass filters were developed to protect your furnace/air conditioning unit, not to improve indoor air quality. Fiberglass filters usually have a MERV rating between 1 and 4. These filters typically sell for about $1 apiece, and they remove less than 10 percent of the air pollutants from your home. For people without allergies and respiratory problems, these filters are fine. If while using a fiberglass filter, you suspect you are having respiratory problems, switch to a pleated filter to remove more pollutants from the air.
Unless you have respiratory problems these low MERV filters are not a problem. Remember that in the spring and fall when the heat and air conditioner are off you are breathing the air in your house with no filtration at all.
Since it takes longer to clog these filters, they should be used in homes where the family will be away for the whole winter since they will not be changed once a month.
Polyester and pleated air filters
Polyester and pleated filters are like fiberglass filters, but they tend to have superior dust-trapping ability. These HVAC filters remove up to 45 percent of the air pollutants in your home. They typically cost around $10 each and have a MERV rating between 8 and 13. For people with respiratory problems this filter will remove most of the contaminants that aggravate your condition. If you are not organized enough to change this filter every month don’t use this type of filter as a plugged filter will shorten the life of your furnace.
High-efficiency air filters
High-efficiency HVAC filters can remove up to 85 percent of the air pollutants from a home or building space. These filters typically sell for $25 apiece and they boast a MERV rating between 14 and 16 (16 is the highest rating).
Often made from pleated filter paper or synthetic polyester fibers, high-efficiency filters can trap very small particles of dust, pollen, mold, pet dander, and other irritants. These filters, however, are not very practical for residential use. Hospitals or other “clean-room” environments use these industrial air filters to even remove bacteria from the air. People with severe respiratory problems may want to use the high efficiency filter, but be sure to change it often so it does not restrict the airflow and damage your furnace.
Keep in mind that the best filter for your heating and air conditioning system might not be the one with the highest MERV rating. An overly restrictive air filter can slow the rate of airflow, causing your unit to malfunction. The ideal air filter is one that has a balance between the least effect on airflow, and one that removes the air contaminants consistent with your respiratory needs.
If you have suggestions for future tips or have questions about maintenance around your home submit them to ask.the.woodchucks@gmail.com
