More than people expect. Air follows the path of least resistance, and a gap offers far less resistance than filter media does — so a disproportionate share of the airflow goes through the gap rather than the filter. It is not a proportional loss. A filter with visible gaps can be doing a fraction of the job you are paying it to do.

People do, and it is better than leaving them open, but it is a workaround rather than a fix. Packing material can shift, come loose into the airstream, or restrict things unevenly. If the correct size simply does not exist as a retail product, having filters made to your dimensions solves it permanently and costs less than repeatedly buying the wrong ones.

Several reasons. Older properties often predate current sizing conventions, renovations change return grille openings, commercial cabinets are built to their own specifications, and high-capacity media housings use deeper filters than consumer ranges cover. None of it is a fault — it just means retail shelves were never going to have your size.

Not automatically. Denser media means more resistance, and too much raises static pressure and reduces the airflow the system needs. We look at blower capacity, duct resistance, and current static pressure before recommending a rating. Getting the fit right is the bigger win; pushing the MERV rating too far can undo it.

We document the dimensions and rating so reordering is straightforward rather than a measuring exercise each time. For commercial properties with several systems, having the sizes recorded per unit is what stops the wrong filters arriving on site — a small piece of admin that saves a surprising amount of bother.

It depends on thickness, rating, and conditions — a deep media filter lasts considerably longer than a one-inch panel. Florida shortens intervals generally, because systems run close to year-round through heavy pollen and coastal air. We will give you a realistic interval for your filter and property rather than repeating the packet.