Roof ridge vent system

A roof ventilation system for asphalt shingle or composition roofs that include a vent slot located through the roof structure along a roof ridge comprising an unrollable vent assembly installable in one piece, the vent assembly including an upper water barrier having first and second vent arrangements connected thereto, each of the first and second vent arrangements having a length and including at least two continuous longitudinal strips of a vent material with a continuous longitudinally extending space therebetween, the strips positionable on the roof parallel to the ridge and having a length equal to the length of the vent arrangements, the strips on a down slope side of each of the vent arrangements having a down slope face area that fills a space between the upper water barrier and the roof in the installed position, the strips of vent material adapted to be along the vent slot having an up slope area having an up slope length and up slope height between the roof and water barrier in the installed position, a water dam connected to the upslope area along the up slope length of the respective up slope areas and having a dam height less than the upslope height, the first and second vent arrangements locatable on each side of the ridge vent slot, respectively, to prevent ingress of moisture and debris, and the upper water barrier above the first and second vent arrangements, extending between the first and second vent arrangements and over the vent slot in the installed position.