To ensure a louver's weather resistance, look for a design that assists in preventing water penetration. This feature uses blades with gutters and internal "downspouts" in the frame to collect and drain rain water before it can become entrained in the airflow. These are known as "drainable" louvers.
To provide the maximum protection against rain penetration, wind driven rain resistant louvers are also available. These models are designed to stop wind-blown rain penetration as well as water entrained in the airflow. They incorporate closely-spaced blades with sophisticated profiles. Although these are more expensive per sq. ft. than other louver types, their ability to prevent water penetration in severe weather is well worth the expense. Wind driven rain louvers can also be made smaller than conventional louvers due to greater water resistance.
Installation methods are just as important as the design of the louver. An important component for the weather resistance of any louver installation in metal buildings is flashing. It is a good idea to flash-off all sides of louver openings in metal wall systems. This prevents water seepage under the exterior skin of the wall system and provides a surface for caulking the louver frames. Larger outside air openings should incorporate a gutter flashing at the top to collect water before it can reach the louver. And, it is a good idea to extend the bottom or sill flashing beyond the back of the louver to capture water that may collect on the bird or insect screen on the rear of the unit.