Abstract: An improved air filter for filtering particulate matter from the air flow of a ventilation system and a method for manufacturing the air filter. The air filter comprises an air filter media having a top surface, a bottom surface, and a perimeter. The filter media preferably is a pleated media. A frame surrounds the perimeter of the media. The frame is preferably made of Styrofoam or similar lightweight foaming material. The foam material becomes bonded to the media such that air leakage between the foam material and the media is prevented when the air filter is in use in the ventilation system. Reinforcing ribs may be provided on the media to provide additional structural support for the filter.