The easiest way to cover your HVAC ducts during construction is to use painter’s tape to affix plastic sheets over your vents and air returns in the area of your home where construction will take place. Keep in mind that closing off a portion of your system can put strain on your blower motor and air handler, so either shut the zone off or shut your system off while construction is underway. If you shut the zone, you can also hang plastic sheets over doorways to separate the construction area and keep dust contained.