AMCA InMotion - September 2019 - 31

Hurricane Florence hits the East coast of the United States in
September 2018. Elements of this image furnished by NASA.
lavizzara/Shutterstock

building codes commonly require special heavy-duty

weather events. While most are tested to ANSI/AMCA

architectural louvers to mitigate rain intrusion and repel

Standard 500-L, they also are tested to one or more

windborne debris.

severe-duty test standards, such as ANSI/AMCA Standard

Just a few years ago, most severe-duty louvers, often

550, Test Method for High Velocit y Wind Driven Rain

referred to as hurricane louvers, were being marketed

Resistant Louvers, and ANSI/AMCA Standard 540, Test

and sold in Florida, which has been at the forefront of

Method for Louvers Impacted by Wind Borne Debris. Because

this market since the late 1990s. In recent years, however,

of the extreme conditions of hurricanes and tropical

more and more states and jurisdictions in hurricane-prone

storms, designed wind loads for severe-duty louvers can

regions have adopted building codes requiring severe-duty

be as high as 160 psf (7.6 kPa).

louvers. To date, these include:
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Connecticut.

Building Risk Categories

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Georgia.

Buildings and other structures are classiﬁed into one of

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Maryland.

four risk categories based on the hazard to human life they

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Massachusetts.

represent in the event of failure:

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New Jersey.

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New York (the state and city).

represent a low hazard to human life in the event of

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Pennsylvania.

failure, such as agricultural and minor storage facilities.

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South Carolina.

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Texas.

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Virginia.

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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.

a severe-duty louver may be needed, testing severe-duty
meet to be applied appropriately.

Risk Category II-buildings and other structures not
listed in risk categories I, III, and IV.

■

This article will discuss circumstances under which
louvers undergo, and criteria a severe-duty louver must

Risk Category I-buildings and other structures that

■

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

Standard Louvers vs. Severe-Duty Louvers
An important part of any healthy HVAC system, louvers
are intended to protect air-intake and exhaust openings

operational during a hurricane or tropical-storm event.
The higher the risk category, the higher the required
design load.

from the ingress of outside elements. Typically, the element
of greatest concern is water.
A standard louver, one that has been tested to ANSI/

Hurricane-Prone and
Windborne-Debris Regions

AMCA Standard 500-L, Laboratory Methods of Testing

The 2012, 2015, and 2018 editions of the International

Louvers for Rating, is intended to perform under normal

Building Code (IBC) deﬁne hurricane-prone region as the

operating conditions-that is, minor to moderate weather

U.S. Atlantic Ocean and Gulf of Mexico coasts where the

events. Systems and buildings protected by these louvers

ultimate design wind speed for Category II buildings is

are expected to remain functional during those events.

greater than 115 mph (51.4 m/s), as well as Hawaii, Puerto

Most standard louvers are designed for wind loads in the

Rico, Guam, the Virgin Islands, and American Samoa.

20-to-30-psf (0.96 to 1.4 kPa) range. This is sufﬁcient for
most buildings in most geographical areas.

Located within hurricane-prone regions are what
the 2012, 2015, and 2018 editions of the IBC deﬁ ne as

Severe-duty louvers are intended to protect building

windborne-debris regions. These are areas: (a) within 1 mile

envelopes and occupants from potentially life-threatening

(1.61 km) of the coastal mean high-water line where the

w w w. a m c a .o r g

20 19 A M CA i n m o t i o n

http://www.amca.org

AMCA InMotion - September 2019

Table of Contents for the Digital Edition of AMCA InMotion - September 2019