Louvers can also be categorized as drainable-blade louvers and non-drainable-blade louvers. Drainable blades are designed with gutters in them that collect water falling on the blade and drain it to the blade ends, where it flows into vertical frame members and is conducted to the exterior. Non-drainable blades allow water falling on the blades to run down the face of the louver. Drainable louvers may be recommended where louvers are connected to ductwork with higher velocity airflows while non-drainable louvers may suffice where air is typically static.
Storm-resistant louvers typically have specially shaped blades that force the airflow to change course as it goes through the louver. The momentum of wind-driven raindrops carries them in a straight line into the louver blades rather than following the redirected air path and then the water is directed in channels to the exterior. Storm-resistant louvers may be expensive and use should be limited to places where wind-driven rain is anticipated, such as hurricane-prone areas.
Louvers may be furnished with galvanized, anodized aluminum, or painted finishes. Baked enamel and siliconized-polyester coatings are typical finishes provided by louver manufacturers. High-performance organic coatings and polyester powder coats are high-end architectural finishes that could match finishes of curtain wall systems and metal siding, and are available as options from some louver manufacturers.
Louvers may have optional bird or insect screening. Insect screens easily clog and should not be used where frequent cleaning will not be routine.
Many different louver configurations are available to suit various needs such as appearance, air performance, weather resistance, acoustic performance, and structural performance under wind, impact, and seismic loads. Selecting specific louvers often requires engineering assistance and should be based on a number of factors, not solely on free area. These performance factors are established by standard test procedures described in AMCA 500-L. Louver depth, overall louver opening size, and the shape and spacing of blades all affect the performance.
