Your house needs to have proper ventilation in order to breath. The attic is where all the heat from the house builds up and is extremely important for the air vapors to be expelled from the house. If this does not occur, this may create mold issues and premature deteriorating shingles. In the winter time, without ventilation, your roof will melt snow and the water will freeze at night which may cause ice dams. Be sure you choose a ridvent that is sturdy and will not compress when cap shingles that are installed on top of the ridge vent because this will choke off the ventilation.