Ever wonder, “Which furnace filter should I use?”
Furnace filters come in a variety of medias. We will cover the difference between the two most common.
Cotton Pleated VS Fiberglass


MERV – Minimum Efficiency Reporting Value, developed by the American Society of Heating, Refrigeration and Air Conditioner Engineers (ASHRAE.) MERV values vary from 1 to 16. The higher the MERV value is, the more efficient the filter will be in trapping airborne particles.
Fiberglass Furnace Filters- The majority of fiberglass filters only stop 2% of the dust passing though your furnace. Often you may notice the filter doesn’t look dirty after months of use. Fiberglass filters can allow particles the size of grains of table salt to pass through. Thus allowing dust to clog your expensive evaporator coils. Dust particles will also collect on the back of the blower motor causing premature failure due to over heating.
Cotton Pleated Furnace Filters - Comfort Zone recommends using standard pleated filters. ( MERV 8 ) These filters are not too restrictive and can be found in 3-packs at Home Depot for as low as $7.00
MERV 8 furnace filters are electrostatically charged, 100% synthetic and cause little to no change in static pressure. MERV 8 filter media will not promote the growth of bacteria, mold, mildew, or fungi in normal operating environments. These filters are designed to last up to 3 months.
4″ Furnace Filters
As efficiency increases, so does the restriction to air flow. To compensate, more filter material is used in pleats. Increasing the square footage of the filter material allows for better air flow and less restriction.
The most common sizes used in heating and air conditioning equipment are 1 inch and 2 inch but are also available in 4 inch, 5 inch and even 6 inches deep. The deeper the pleat the greater the dust holding capacity and the longer it can remain in the air handler without needing to be changed.
Comfort Zone recommends changing a 4″ cotton pleated furnace filter every 6 months.