I have a Perfect Fit air filter that was put in when I replaced my AC with a Trane Heat Pump last year. It defintely works better than the previous one, but the replacement filters are hard to find, relatively expensive, and are needing to be replaced quite often. They are 5 inches thick.
Is 5 inches thick better than the standard 1 inch thick filters? If so, can you explain?
If not, do you think I could just put a frame inside that would close down the opening to be 1 inch thick to use more standard filters and not lose in performance or worry about problems with it.