HVAC & Furnace Filters: Home Air Quality Guide

HVAC filters are rated on the MERV scale (Minimum Efficiency Reporting Value) from 1-16. MERV 8 captures common household dust, pollen, and mold. MERV 11 adds pet dander and smog particles. MERV 13 captures bacteria and smoke. For most homes, MERV 11 is the optimal balance of filtration and airflow.

Filter dimensions must be exact. Measure the width, height, and depth of your existing filter or check the size printed on its frame. Common residential sizes include 16x25x1, 20x20x1, and 20x25x4. Using an incorrect size allows unfiltered air to bypass the filter entirely.

The 1-inch vs. 4-inch debate: standard 1-inch filters are cheaper but need monthly replacement. 4-inch (or 5-inch) deep-pleated filters cost more upfront but last 6-12 months and provide better filtration with less airflow restriction. If your system supports a 4-inch filter housing, it's the better long-term investment.