Attic ventilation is an important part of roofing. Proper attic ventilation extends the life of a roof and reduces problems because it minimizes the temperature differential between the attic and air outside. Proper ventilation will remove moisture and heat from the attic. A balance circulation system will have one square foot of venting for every 300 cubic feet of free air in attic. This ratio is used to find how many vents you need. You should have an equal distribution of intake (soffit) and out-take (roof) vents for circulation to be effective. Intake vents which are located at the underside edge of roof, known as eaves; allow fresh air flow in the attic. Exhaust vents which are located near the ridge (top crest) or directly on the ridge line of the roof, depending on the vent type; allow the air to leave the attic. Both intake and exhaust vents must be in place, and unobstructed in order for system to work.