Cover the unused HVAC vent with a large piece of furniture. Place a dresser or desk over a floor vent or conceal a wall vent with a hutch, solid book shelf or tall China cabinet.
Use a room-dividing screen that folds to cover the unused HVAC vent. Position it so it covers either the wall or floor unit. Select one that blends with the room as part of the decor.
Cover an unused HVAC vent in the ceiling by creating a custom fabric cover. Measure the area around the vent and add 1 inch to both the length and width. Cut a piece of fabric based on the measurements. Use a staple gun to attach the fabric to the ceiling around the vent.
Measure the perimeter of your wall, ceiling or floor HVAC vent and add 2 inches to each side. Cut a piece of plywood in the shape of the vent, based on measurement. Finish the plywood to match the floor, ceiling or wall. Position it over the vent and drive a nail through each corner of the wood to secure.