Why Change The Filter?
Keeping a clean furnace filter is the most important step in keeping a long lasting efficient HVAC system. The most important purpose of the filter is in fact to protect the furnace and air conditioner from harmful dust and dirt that can burn up on the furnace heat exchanger and clog up the air conditioner coil. It's a fact that changing the filter regularly will greatly reduce energy cost, reduce equipment failures and prolong the life of the equipment.
The 1# cause of furnace and AC system failures are due to a dirty air filter!
In heating season when the filter is very dirty the furnace will over heat causing parts to fail or even crack in the heat exchanger which can lead to to harmful gases expelling into the home.
In the cooling season a dirty air filter can cause your AC coil to freeze. This ice will eventually melt and often lead to water damage in the furnace room and surrounding areas and causing your AC to fail.
The Merv 8 filter is the best choice for a standard 1" thick filter, Anything less Is not stopping small particles and anything higher is to strenuous on the HVAC equipment. If you want a higher Merv rated filter example. 10-13 you should have a 2-5" thick filter in order for the filter to have enough surface area to ensure you get proper air flow. If your furnace was installed with a standard 1" filter and you're looking for a cleaner air, consider having an external air cleaner installed or having a local service company install a larger filter cabinet.