Measure the width and length of the existing soffit vents. Standard soffit vents are typically 4, 6 or 8 inches wide and 16 inches long. The roofing contractor determines the size and the number of vents to install by figuring the square feet of floor space in the attic. Purchase the same size vents.
Remove the old soffit vents with a drill fitted with a screwdriver bit.
Position a new dampered soffit vent in the exact spot where you removed the old vent, turning the louvered vents to face the house. Before attaching the new vent, turn the knob on the face of the vent to see how the damper plate opens and closes.
Insert the screws that came with the vent, using the drill and the screwdriver bit. Replace all the old vents in the same manner.
Turn the knob or handle, located on the center of the soffit vent to open and close the damper.