The Condenser - Louver Blade Angle

How does a louver's blade angle affect its performance? Why is blade angle important? Learn what it means for your louvers with this quick Condenser article.

Although blade spacing is important, it is just one aspect of louver blade design. In this Condenser, we will look at louver blade angles and how they relate to airflow performance.

What is a blade angle?

Blade angle is the angle of the louver’s blades in relation to the face of the louver. The higher the angle, the higher the incline of the blade. Louvers will typically have a blade angle between 30 degrees and 47 degrees.

Blade angle will be consistent across the louver's face. Even adjustable louvers will maintain a consistent blade angle when fully open. Certain specialized louvers will use blades of different angles. For example, an intake-exhaust louver will have 35-degree blades for its intake zone and flat 90-degree blades for the exhaust zone. 

Why does blade angle matter?

A higher blade angle generally means better water rejection. The steeper incline makes it easier to capture rain drops as they pass through the louver. Raindrops are heavier than air. As air moves across the blade, the heavier raindrops in the air stream won't make it up the incline. The lighter air continues flowing through the louver. As the airstream slows, the rain drops slide off the blade. 

Blade features like catches can help reject rainfall. Wind driven rain louvers will use drainable features with a high blade angle for excellent protection. However, this protection can come with a price. Blade angle will affect the louver’s pressure drop. That means the system will expend more power to draw air through the louver.

High-angle blades create more resistance. The difference in resistance may seem minor, but if your goal is efficiency, then you should consider the louver’s blade angle. A lower blade angle will provide more airflow for the same power.

This is a rule of thumb. Remember that blade angle is just one aspect of the louver’s design. Other factors will also play into the louver’s performance. Blade profile, drainable features, and free area will also affect how the louver performs.

The best indication is performance data. Check the louver’s submittal for pressure drop and water penetration data. Use this data to determine if the louver will work for your application.

For more on louvers, check out these Newsstand articles:

• Louver Blades - A Primer
• Three Common Types of Intake Louvers
• The Condenser - Water Infiltration and Louvers
• AMCA Testing for Louvers - Water Penetration