I would always prefer that you use a 1" filter and that you use a cheap fiberglass filter like the one below. Anything pleated can and will cause limit faults.In my experience even the 4" media filters raise static pressure and temperature rise.
If you are using a 1" thick pleated air filter you may be asking for trouble. Some homes were built with unsatisfactory ductwork. If you have undersized duct for the size of your furnace you may be compromizing the life of your heat exchanger by running these very restrictive filters. The higher the merv rating, the more restrictive your filter will be. If you need better filter performance do to allergies, do not buy these expensive pleated 1" filters. Spend your money on a 4" wide media filter at the very least if you require better filter performance due to allergys. These air filters provide much more filtering area and don't need to be changed for 6 months to a year.
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