FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

Volume II Designing the builDing envelope 11
Wind-borne debris also occurs in the portions of hurricane-prone regions that are inland of wind-borne
debris regions, but the quantity and momentum of debris are typically lower outside the wind-borne debris
region. As a conservative measure, impact-resistant glazing or shutters could be specifed inland of the windborne
debris region. If the building is located where the basic wind is 125 mph 8 or greater and is within
a few hundred feet of a building with an aggregate surface roof or other buildings that have limited wind
resistance, it is prudent to consider impact-resistant glazing or shutters.
With the advent of building codes requiring glazing protection in wind-borne debris regions, a variety of
shutter designs have entered the market. Shutters typically have a lower initial cost than laminated glass.
However, unless the shutter is permanently anchored to the building (e.g., accordion shutter, roll-up shutter),
storage space is needed. Also, when a hurricane is forecast, the shutters need to be deployed. Te difculty of
shutter deployment and demobilization on upper-level glazing can be avoided by using motorized shutters,
although laminated glass may be a more economical solution.
Because hurricane winds can approach from any direction, when debris protection is specifed, it is important
to specify that all exterior glazing be protected, including glazing that faces open water. At the house shown
in Figure 11-10, all of the windows were protected with roll-up shutters except for those in the cupola. One
of the cupola windows was broken. Although the window opening was relatively small, a substantial amount
of interior water damage likely occurred.
COASTAL CONSTRUCTION MANUAL
Figure 11-10.
Unprotected cupola
window that was broken.
Estimated wind speed:
110 mph. Hurricane Ike
(Texas, 2008)
Te FBC requires exterior windows and sliding glass doors to have a permanent label or marking, indicating
information such as the positive and negative design pressure rating and impact-resistant rating (if applicable).
Impact-resistant shutters are also required to be labeled. Figure 11-11 is an example of a permanent label on
a window assembly. Tis label provides the positive and negative design pressure rating, test missile rating,
8 The 125-mph basic wind speed is based on ASCE 7-10, Risk Category II buildings. If ASCE 7-05 or an earlier version is used, the
equivalent wind speed trigger is 100 mph.
11-11