What type filter should you use?

This is one of the most common questions that I get from homeowners. The choice has a lot to do with the size of the return on your unit. The return is the void where you replace your filter. The general rule is that the system should have at least 160 square inches of return space per ton. Ideally you want 200 square inches per ton, but sometimes space is limited. You can calculate the amount of return space by simply multiplying the dimensions of your filter. If you have a 12x24 filter then you have 288 square inches.  I use this size simply because this is the most common size in homes that I service. But, you can do this calculation for any size filter grill. A 20x25 filter has 500 square inches. One important thing to remember is that you can never have too much return space but it is very easy to have too little return space. If you find that your filter is as much as or equal to the 160 square inches per ton number then you should safely be able to use a pleated panel filter.  If you find that your filter is less than the 160 square inches per ton number then you should consider increasing the size of your return or adding an additional return grill. If this is not feasible due to space restrictions then you should consider using a fiberglass filter. Although, keep in mind that these filters do not capture as much dust and debris as a pleated panel filter.