Date: 2019-08-29 16:52:00
Hurricane Florence hits the East coast of the United States in September 2018. Elements of this image furnished by NASA. Credit: lavizzara/Shutterstock
With climate change influencing and expected to worsen the frequency, intensity, and impacts of extreme-weather events,1 more and more states and jurisdictions are adopting building codes requiring severe-duty louvers. Here’s what you need to know.
Note: This article appears in the 2019 edition of AMCA inmotion magazine.
By JAMES K. SMARDO and DOUG PETTY, AMCA Louver Marketing Task Force, and SCOTT ARNOLD, AMCA International
In September, when this article is published, the Atlantic hurricane season, which officially begins June 1 and runs until Nov. 30, with most of the storms hitting between August and October,2 will be at its peak. Following a 2018 season that was more active than expected,3 with 15 tropical storms and eight hurricanes, two of which—Florence and Michael—were “major” (Category 3, 4, or 5),4 forecasters predicted5 the 2019 season to be “near normal” (10 to 15 tropical storms and four to nine hurricanes)2 to slightly “above normal” (12 to 28 tropical storms and seven to 15 hurricanes)2 with 12 to 14 storms, including five to seven hurricanes and two to four major hurricanes.5
Hurricanes are the most violent storms on Earth, capable of producing wind speeds of up to 190 mph (306 km/h). Resulting rain intrusion and impact damage from airborne debris can be catastrophic to a building and a danger to its occupants. In geographical areas where these storms are most likely to occur, known as hurricane-prone regions, building codes commonly require special heavy-duty architectural louvers to mitigate rain intrusion and repel windborne debris.
Just a few years ago, most severe-duty louvers, often referred to as hurricane louvers, were being marketed and sold in Florida, which has been at the forefront of this market since the late 1990s. In recent years, however, more and more states and jurisdictions in hurricane-prone regions have adopted building codes requiring severe-duty louvers. To date, these include:
- New Jersey.
- New York (the state and city).
- South Carolina.
This article will discuss circumstances under which a severe-duty louver may be needed, testing severe-duty louvers undergo, and criteria a severe-duty louver must meet to be applied appropriately.
Standard Louvers vs. Severe-Duty Louvers
An important part of any healthy HVAC system, louvers are intended to protect air-intake and exhaust openings from the ingress of outside elements. Typically, the element of greatest concern is water.
A standard louver, one that has been tested to ANSI/AMCA Standard 500-L, Laboratory Methods of Testing Louvers for Rating, is intended to perform under normal operating conditions—that is, minor to moderate weather events. Systems and buildings protected by these louvers are expected to remain functional during those events. Most standard louvers are designed for wind loads in the 20-to-30-psf (0.96 to 1.4 kPa) range. This is sufficient for most buildings in most geographical areas.
Severe-duty louvers are intended to protect building envelopes and occupants from potentially life-threatening weather events. While most are tested to ANSI/AMCA Standard 500-L, they also are tested to one or more severe-duty test standards, such as ANSI/AMCA Standard 550, Test Method for High Velocity Wind Driven Rain Resistant Louvers, and ANSI/AMCA Standard 540, Test Method for Louvers Impacted by Wind Borne Debris. Because of the extreme conditions of hurricanes and tropical storms, designed wind loads for severe-duty louvers can be as high as 160 psf (7.6 kPa).
Building Risk Categories
Buildings and other structures are classified into one of four risk categories based on the hazard to human life they represent in the event of failure:
- Risk Category I—buildings and other structures that represent a low hazard to human life in the event of failure, such as agricultural and minor storage facilities.
- Risk Category II—buildings and other structures not listed in risk categories I, III, and IV.
- Risk Category III—buildings and other structures that represent a substantial hazard to human life in the event of failure, such as grade schools and theaters.
- Risk Category IV—buildings and other structures designated essential facilities, such as hospitals and police, fire, and rescue stations, which often are intended to remain operational during a hurricane or tropical-storm event.
The higher the risk category, the higher the required design load.
Hurricane-Prone and Windborne-Debris Regions
The 2012, 2015, and 2018 editions of the International Building Code (IBC) define hurricane-prone region as the U.S. Atlantic Ocean and Gulf of Mexico coasts where the ultimate design wind speed for Category II buildings is greater than 115 mph (51.4 m/s), as well as Hawaii, Puerto Rico, Guam, the Virgin Islands, and American Samoa.
Located within hurricane-prone regions are what the 2012, 2015, and 2018 editions of the IBC define as windborne-debris regions. These are areas: (a) within 1 mile (1.61 km) of the coastal mean high-water line where the ultimate design wind speed is 130 mph (58 m/s) or greater or (b) where the ultimate design wind speed is 140 mph (63.6 m/s) or greater.
ANSI/AMCA Standard 550
ANSI/AMCA Standard 550 establishes uniform test methods and minimum performance ratings for the water-rejection capabilities of louvers intended for use in high-velocity winds, including hurricane-like conditions.
In the performance of an ANSI/AMCA Standard 550 test, a fan positioned in front of a louver test specimen simulates wind speeds of 35, 70, 90, and 110 mph (15.6, 31.3, 40.2, and 49.2 m/s), while water nozzles positioned between the fan and louver test specimen simulate horizontal driving rain at a rate of 8.8 in. (223.5 mm) per hour. Each test is performed for 15 min, with the exception of the 110-mph (49.2 m/s) test, which is performed for 5 min.
Unlike ANSI/AMCA Standard 500-L water-penetration and wind-driven-rain tests, ANSI/AMCA Standard 550 tests do not simulate air being pulled through louvers from behind. However, any louver tested to ANSI/AMCA Standard 550 must have undergone the ANSI/AMCA Standard 500-L wind-driven-rain test.
The ANSI/AMCA Standard 550 test is pass/fail. Failure occurs when more than 1 percent of the total volume of water sprayed penetrates the louver. (It is important to note that this can be considered a substantial amount, as much as 2-plus gal. [7.5-plus L], depending on the louver. A distinction should be made between this test and the water-penetration test defined in ANSI/AMCA Standard 500-L, which tells only the point at which water will be drawn behind a louver.) The standard allows fixed-blade (open) louvers, operable-blade louvers, and combination louver/operable dampers. Any operable-blade product tested in the closed position must be clearly identified as such in product test reports, product submittals, and installation instructions.
ANSI/AMCA Standard 540
ANSI/AMCA Standard 540 establishes uniform methods for testing a louver’s resistance to large missiles as described in ASTM E1996-04, Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Windborne Debris in Hurricanes, and ASTM E1886-05, Standard Test Method for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Missile(s) and Exposed to Cyclic Pressure Differentials.
In an ANSI/AMCA Standard 540 test, a 9-lb (4,100 g) 2-in.-by-4-in. piece of lumber is fired at a louver specimen at a rate of 50 fps (15.25 m/s) in an evaluation of Missile Level D (basic) protection, which most Risk Category I, II, and III facilities call for, and at a rate of 80 fps (24.38 m/s) in an evaluation of Missile Level E (enhanced) protection, which Risk Category IV facilities require.
ANSI/AMCA Standard 540 requires that a test specimen be impacted in three specific locations, including blade edge and centerline. If a multi-wide or multi-high assembly is being considered, any vertical or horizontal mullion conditions also must be impacted.
Like the ANSI/AMCA Standard 550 test, the ANSI/AMCA Standard 540 test is pass/fail. Failure occurs if the missile penetrates the innermost plane of the louver test specimen and any adjacent components lose fastener/weld connection or if the missile leaves an opening through which a 3-in.- (76 mm) diameter solid sphere could pass.
Specifying Louvers in Hurricane-Prone Regions
Since 2012, the International Mechanical Code has been requiring louvers in hurricane-prone regions to be ANSI/AMCA Standard 550-compliant, while the IBC has been requiring louvers in windborne-debris regions that are within 30 ft (9,144 mm) of grade to be ANSI/AMCA Standard 540-compliant.
To safeguard against inappropriate product substitutions, design professionals are advised to include in their specifications language similar to the following: “Louvers shall be licensed to bear the AMCA listing label for high-velocity-rain resistance in accordance with AMCA Publication 512” (AMCA Listing Label Program). AMCA Publication 512 outlines a program assuring products were tested at an AMCA-accredited laboratory and performed as specified.
When specifying a louver, determining which codes to follow can be difficult. The International Code Council (ICC) offers guidelines, but does not mandate testing. Agencies such as AMCA, the Florida Building Commission, and the Miami-Dade County Department of Regulatory and Economic Resources all participate in certifying louvers in Florida. The Federal Emergency Management Agency offers guidelines for testing, but does not verify.
Although Miami-Dade approval has been considered the default standard for louvers in hurricane areas—even those outside of Florida—for years, it is not required by code anywhere but in Florida high-velocity hurricane zones. ANSI/AMCA Standard 540 and ANSI/AMCA Standard 550 are required by the ICC in hurricane areas everywhere.
To ensure proper compliance and to learn of any special circumstances, designers and specifiers are advised to check with local authorities.
By specifying louvers that bear the AMCA listing label for high-velocity-rain resistance in hurricane-prone regions and the AMCA listing label for impact resistance in windborne-debris regions, design professionals can rest assured knowing their specifications comply with building-code requirements.
- C2ES. (n.d.). Extreme weather and climate change. Retrieved from http://bit.ly/C2ES_ExtremeWeather
- Ghose, T. (2019, May 23). Hurricane season 2019: How long it lasts and what to expect. Live Science. Retrieved from http://bit.ly/Ghose_Hurricane
- Why the 2018 hurricane season was more active than we predicted. (2018, November 29). Retrieved from http://bit.ly/Hurricanes_2018
- Destructive 2018 Atlantic hurricane season draws to an end. (2018, November 28). Retrieved from http://bit.ly/NOAA_Hurricanes2018
- MacMath, J. (2019, April 4). AccuWeather’s 2019 Atlantic hurricane season forecast. Retrieved from http://bit.ly/AccuWeather_2019
About the Authors
James K. Smardo is director, architectural sales, for Ruskin and chair of AMCA’s Louver Marketing Task Force. Doug Petty is product manager, louvers, for Pottorff and All-Lite Architectural Products and a member of AMCA’s Louver Marketing Task Force. Scott Arnold is manager of industry content for AMCA International and editor in chief of AMCA inmotion.