Finding the Right Storm Louver

Your building should be protected throughout the year, whether it rains or shines. MCDLG can help you find the right storm louvers for your project. Learn more on the Newsstand.

Selecting the right Storm Louver

Louver selection is a balancing act between performance and protection, while meeting requirements. You need a louver that has a minimal impact on system performance while providing the best possible weather protection. It should meet the project’s requirements at a minimum. 

Storm louvers prioritize protection, keeping interiors dry and safe, but they must also provide adequate airflow. How do you select the right storm louver for your project? The answer requires understanding the needs of your project.

Determine Protection Level

The term “storm louver” includes several louver types: drainable louvers, wind driven rain louvers, hurricane louvers, and FEMA louvers. These louver types provide varying degrees of protection, depending on the need. They are all designed to guard against water infiltration.

Start by determining the required level of protection. What do you need the louver to do? These questions can help point you in the right direction:

• Is heavy rain common in your region? Certain louvers are better equipped for rejecting rain, like blade troughs for draining excess water.
• Do you expect severe weather? Weather patterns will differ from season to season, but your building should always be prepared for the worst scenario.
• Is the project in a hurricane prone area? Coastal regions require louvers that meet hurricane standards. Manufacturers build hurricane louvers for severe weather, for hurricane requirements only.
• Will the project be a storm shelter? FEMA louvers are heavy-duty louvers built to endure tornados and other extreme weather. These louvers protect openings in storm shelters. 

Choose louvers that fit the requirement. If the project requires wind driven rain protection, choose a louver rated for wind driven rain.

The key is to find a storm louver that will protect your project throughout the year. It’s best to lean towards more protection, so that the building is prepared for unexpected shifts in weather.

You may decide to use wind driven rain louvers instead of standard drainable louvers. This would be a good upgrade for a storm louver. Wind driven rain louvers will keep the interior dry all year. Hurricane louvers may seem like the next step up in protection. While they meet tougher standards, hurricane louvers should only meet hurricane requirements. 

Make sure your storm louver also meets airflow requirements. You don’t want the louver to be a drag on your HVAC system.

Check for AMCA Seals

AMCA stands for the Air Movement and Control Association. AMCA establishes the standards for testing air movement and control products. This includes louvers and dampers used in HVAC systems. All storm louvers will have AMCA certified ratings seals.

These seals indicate that an AMCA-approved laboratory tested the louver under AMCA standards. Read more about these seals in this Newsstand article. 

To summarize, louvers receive an AMCA seal when they complete tests performed in an AMCA-approved laboratory. The seal is not a signifier of performance.

A ratings seal for Wind Driven Rain means that the louver has completed the tests for wind driven rain, in accordance with AMCA Standard 500-L. It also means that the wind driven rain data printed on the submittal is reliable. To understand its performance, you will need to review the data on the louver’s submittal.

Review Test Data

Submittals are important documents that describe the louver. Each submittal contains everything you need to know about a specific louver:

• the materials used to build the louver,
• the minimum and maximum sizing of a louver panel,
• options and accessories,
• and test data.

Test data is important for understanding how a storm louver will perform. Remember, every AMCA seal corresponds to one or more tests that the louver has completed. Each test targets a specific louver characteristic.

Water penetration testing and wind driven rain testing may seem like the same test. Both tests examine the louver’s capability to deflect rainfall while air is moving through the louver. However, the tests target unique characteristics.

Water penetration testing determines the first point, in intake air velocity, when water infiltration occurs. Exceeding this velocity will cause rain to pass through the louver. A higher water penetration starting point is better, but it doesn't show the amount of water rejected. Wind driven rain testing applies a second air stream that pushes against the louver face, which determines the louver's ability to reject rain blown against the louver by high winds. This test also measures the amount of water rejected by the louver and assigns an effectiveness rating at multiple stages throughout the test.

Both tests provide important insights into the louver’s capabilities. We often test storm louvers for water penetration and wind-driven rain to display both data sets on the louver submittal. Air performance testing is also important, because it measures pressure drop as air passes through the louver’s free area. This will help you determine the louver’s impact on airflow and energy requirements for the system.

Determine the maximum velocity of intake air first. Does this value exceed the beginning point of water penetration? Does the wind driven rain data show excessive water infiltration at this velocity? If so, then the louver may not protect the opening during a storm. Know the conditions of the application and you will clearly understand how the louver works.

Determine Sizing

The primary purpose of a storm louver is to protect the space behind it, whether that space contains a length of ductwork or a room. It should fully cover the opening. Manufacturers can create multi-panel louvers for covering larger openings.

However, larger louvers will perform differently than smaller louvers. AMCA tests a standard 48” x 48” single-panel louver. The test data you see on the louver’s submittal will be for the standard size. Large louvers will typically have more space between their blades than smaller louvers. This space, the louver's free area, allows air to move through the louver and more space is better for air performance. However, it can also affect the louver's ability to reject rain.

The difference in protection will be negligible many times, but it may become an issue as the louver approaches its maximum panel size. Manufacturers can help you determine if a specific louver will meet your requirements at a larger size.

Storm louvers protect your building from rain and other storm hazards. By understanding what you need, you can choose the best louver to meet your project’s needs.

Arrow United Industries can help you with your storm requirements. We build severe weather louvers for advanced storm protection. Contact us today and start your next project with the right louvers.

Have you ever replaced standard louvers to meet severe weather requirements? Tell us about your experiences in the Comments section. We want to hear from you!

Learn more about louvers with these Newsstand article:

• Hurricane Louvers and Severe Duty Protection
• Four Questions on Louver Location
• The Condenser - Water Infiltration and Louvers