Abstract: A register cover (also referred to as a vent cover) for use in a building that has heating, ventilation and air-conditioning (HVAC) systems that utilize air registers. The register cover completely covers the register and secures to the register using a magnet in order to substantially block the flow of forced air through the register that is covered by the register cover. In the case of a non-metallic register, a method is disclosed for retrofitting the non-metallic register by placing metallic mounts on the register in order to secure the register cover over the register with one or more magnets.