Abstract: The present invention relates to a protective barrier adapted to fit over a roof vent, particularly an off-ridge roof vent, which provides for ventilation and also restricts pass-through of wind-driven rainwater. The barrier comprises two parallel orifice plates, such as louvered panels with passages, that are spaced apart a desired distance by a stagnation zone, so that the device is effective to reduce or eliminate of passage of wind-driven rainwater to the interior of the vent. In various embodiments, the number of louvers in the more outward-disposed orifice plate is greater than the number of louvers in the more inward-disposed orifice plate.