Upgrade filter element on rooftop a/c?
I'm not a fan of the open cell foam sheet commonly used as a filter on travel trailers and motorhomes, so I purchased a couple of these thin poly fiber sheets and cut one to fit each of my ceiling return air covers. I left the foam in place to catch the big pieces and the poly does an excellent job of trapping dust (I can clearly see the dirty spots where the air is passing thru.) However, the volume of air coming out of the ducted vents feels significantly less than with the standard configuration. Intuitively I should expect less flow with the added restriction, but I wonder if it's detrimental to the life of the unit or if it's worth the trouble -- just for the sake of cleaner air and a cleaner evap coil.