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Louver Blades - A Primer

This article examines the various types of louver blades and how these blades work for their intended application. Learn how the blade makes the louver.

Louver blades are the most important part of a louver. Blades allow air to pass between them and keep undesirable elements out. A louver’s blades will determine the louver's capabilities. The blade's design dictates whether it will work best as an airflow louver, a rain resistant louver, an acoustical louver, a sight proof louver, or any other kind of louver. Each blade will have various features that differentiate one blade type from another. These features are known as the blade's profile.

There are several different types of blade profiles and each is best suited for a specific function: air performance, water penetration, vision blocking, etc.

We will look at the various louver blade types, examine their profiles, and learn what each blade type does best.

Consider taking our self-paced course for a complete explanation of louvers and their mechanics: "An Introduction to Louver Selection." Visit the MCDLG Campus portal for more information.Visit AEC Daily to see MCDLG Online Courses

Drainable and Non-Drainable


Drainable BladeDrainable Blades

Drainable blades are designed to carry excess water out of the louver. These blades have special gutters fixed to the front, designed to catch water as it rolls off the blades. The gutters lead to special channels in the louver’s jambs that drain the excess water down the sides of the louver and out the sill. By controlling the flow, drainable blades lower the risk of water penetrating the louver.


Non-Drainable BladeNon-drainable Blades

Non-drainable blades do not have gutters. These are considered the standard blade type for air control louvers. Gutters affect air performance by creating places for air to drag. By removing these gutters, non-drainable blades allow air to pass into the louver without resistance.

A non-drainable blade can still block water from entering a louver. However, without gutters, the excess water will simply roll off the blades. This can create a waterfall effect on the louver’s face: water from higher blades falling onto lower blades, which collects and falls onto the bottom blades, creating a major excess of water at the bottom of the louver.


Blade Profiles

Straight Blade

Straight Blades

Also known as J blades, straight blades are flat along the blade’s surface. This design is the best for ventilation, because it has no features or catches to resist airflow. Adding features to a blade affects the louver’s air performance. Without these, air can pass freely through the louver, which lowers the louver’s pressure drop. At higher blade angles, straight blades can block water penetration and can effectively remove excess water with drain gutters.


Baffle BladeBaffle Blades

Also known as K blades, baffle blades start flat at the louver’s face, but have a raised portion towards the back of the louver like a stair step. These raised portions create catches that capture moisture before it passes through the louver. When equipped with a drain gutter, baffle blades are effective at stopping water penetration. However, these catches will affect the louver’s pressure drop and overall air performance.


ChevronChevron Blades

Chevron blades come in different shapes – inverted V, inverted Y, and inverted Z – but each design serves a similar purpose. Chevron blades have an upward curve at the center of the blade, creating a wave design through the louver free area. This wave design creates a pathway for airflow and a natural catch for moisture. As air passes over the curve, heavier water particles slide down the incline of the blade. Chevron blades can also have catches to stop moisture if it passes over the curve, adding another barrier for water penetration.

Sight Proof


Sight Proof

Chevron blades can also act as sight proof blades. Their curved design creates a visual barrier between blades, effectively concealing the interior spaces behind the louver.

Sight proof blades are often used in areas that require concealing an interior space. They are commonly used in elevated openings, where passersby could see through the blades of a standard louver.



Acoustical Blades

Acoustical blades are specialized louver blades that contain sound insulation material which dampens loud noises behind the louver. These blades are much thicker than a standard blade. They require a large frame.

Acoustical blades are often used in areas with heavy machinery -so that the noise doesn’t bleed through to outside spaces - while providing ventilation to the equipment inside. In other words, acoustical louvers keep the noise pollution from spreading.


Adjustable Blades

AdjustableAdjustable blades can be adjusted to meet changing air conditions. These blades are connected together with a linkage, which allow all blades to open or close at the same time.  In some cases, they are also called operable blades.

With an actuator installed, these blade can open or close the louver automatically for a variety of HVAC scenarios. Adjustable blades can be drainable or non-drainable, depending on their required function.

In combination adjustable louvers, stationary blades are installed on the face of the louver and the adjustable blades are situated behind them. This allows the louver to close while still maintaining the horizontal lines of the stationary blades.


The Blades make the Louver

Louver Blade ProfileEach blade's shape and its features define how the louver will perform. Blades with catches will block water penetration, but will have lower air performance than a straight blade. Drainable blade gutters also affect air performance, but direct excess water out of the louver and increase the louver's water blocking capabilities.

It all depends on what you need the louver to do. By knowing the louver's primary purpose, you will have a better idea of which louver blades will work best for the task.


Which louver blades work best for your next project? Do you think there are any blade types that will work better for your current buildings? Share your thoughts about louver blades in the Comments section. We want to hear from you! 

MCDLG & Continuing Education

Continuing Education - Transparent Book (Square)MCDLG offers free self-paced courses online through AEC Daily. 

Our louver course, Louvers for Style and Aesthetics, goes over the basic stats, terms, and principles involved in choosing louvers for any application. You will also learn how louvers can enhance your project's style. 

Visit AEC Daily to browse our online courses

This course provides continuing education credits for a variety of institutions, including AIA's LIUs. Learn the basics of louvers and earn credit, at your own pace. Visit the MCDLG course page on today!

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