An important consideration for a furnace retrofit is the filtration system comprised of the furnace filter cabinet and filter media. The filter cabinet should provide a positive door seal and should be well sealed to eliminate any air bypass around the cabinet or filter. This will reduce dust particulates building up in the secondary heat exchanger increasing furnace longevity and reducing energy use. The filter cabinet should also be easily accessible and non-obstructed, so that the filter can be easily replaced without bending or damage occurring. A quality filter media should be selected with the homeowner that matches their design requirements (filter efficiency). Thick, pleated filter media with more surface area take longer to load up as compared to thinner filters. This will result in reduced filter replacement. Some heating system thermostats can be programmed to remind the homeowner to replace the filter near the end of the filter's service life.'