Furnace Filters January 1, 2017 ryw Furnace, HVAC, Tips Remember to clean or replace filters on furnaces once a month, or as needed. Related Posts Pan Flashing Pan flashing under doors and windows is an effective way of ensuring that no water is driven under the door or window. Waterbed Savings Keep waterbeds covered with quilts or blankets to help retain their heat. You might also want to insulate the bottom with a sheet of rigid foam insulation. Changing Bits Never change your drill and router bits without first disconnecting the power cord.