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Hurricane-resistant skylights, windows & doors: choices, protection methods, construction, standards & codes. Here we provide a guide to hurricane, storm, and wind resistant windows and skylights, including citing storm resistance standards, building codes, and products.
Guide to Hurricane, Wind, & Storm-Resistant Windows
In this article series we discuss the selection and installation of windows and doors, following best construction and design practices for building lighting and ventilation, with attention to the impact on building heating and cooling costs, indoor air quality, and comfort of occupants.
Page top photo: hurricane resistant windows required in Boca Raton, FL and at left in Jupiter Florida.
We review the proper installation details for windows and doors, and we compare the durability of different window and door materials and types.
In response to the devastating impact of Hurricane Andrew
in 1992, Florida enacted stringent codes to protect homes
from severe storms.
Other coastal states have followed suit
in recent years, and now similar provisions in the International
Residential Code (IRC) apply to coastal areas from
Texas to Maine.
Protect the Window Openings
Researchers attributed much of
Andrew’s destruction to wind penetration into homes
through broken doors and windows, leading to extensive
water damage and, in many cases, roofs blown off and
Our photo (left) shows storm-exposed beach-front hotel windows at Boca Raton, FL.
The keys to preventing these problems
were strengthening roofs and protecting windows and
doors from wind and wind-borne debris. To protect
windows, the new code allows three options:
9/16-inch plywood panels screwed
over windows at 8 inches on-center, or
The trend in new home construction is toward
impact-resistant windows, sometimes marketed as “storm resistant”
Miami-Dade County Standards for Storm-Resistant Windows
enacted the most stringent standard and test protocols,
subjecting windows (and storm shutters) to a test in which a
9-pound 2x4 is hurled into the glass at 50 feet per second,
followed by 4,500 cycles of positive and negative wind
loads equivalent to a 146-mph wind.
Miami-Dade also conducts
AAMA/NWWDA testing for design pressure and
water intrusion, but it conducts the water intrusion test after
the structural test is completed rather than on a new window.
Windows and doors that pass the Miami-Dade Product Control
Standards are required throughout Miami-Dade County
and most other coastal areas in Florida.
International Residential Code for Impact-Resistant Windows
Residential Code (IRC) requires impact-resistant windows
in all hurricane-prone regions along the Gulf and
Atlantic coasts from Texas to Maine. Depending on the
wind-speed zones established in the IRC, windows need
to meet design pressures ranging from 30 to 80 psf, and
they must meet impact-resistance standards under ASTM
E1886 or E1996.
The design pressure required depends
on both an area’s design wind speed, found on IRC maps,
and the building’s exposure rating from A to D. Most
buildings are rated Exposure B for “urban and suburban
areas or wooded areas” or Exposure C for flat, open
terrain with scattered obstructions of less than 30 feet.
Waterfront buildings exposed to winds flowing over open
water for at least a mile are rated Exposure D, the most
Storm-Resistant Window Construction
Under pressure from both the
building codes and insurance industry, most major window
manufacturers have developed impact-resistant windows
for residential applications that feature laminated
glass along with heavier frames and hardware. The glass
is similar to auto windshields with a plastic interlayer, but
it is significantly heavier. Double-glazed units get a
second layer of tempered glass either on the interior or exterior.
Vinyl-framed windows are heavily reinforced with
aluminum, and all windows use metal mullion bars anchored
to the framing between mulled units. Window-to framing
attachment methods are also beefed up to comply
with the new codes, and in some cases, metal clips are
used to anchor the window to the frame.
windows cost from two to four times as much as standard
windows; but under pressure from code agencies and
insurance companies, these windows will soon become
standard fare in coastal construction and other storm-prone
Performance Grade and Design Pressure for Windows
well a window performs when subjected to heavy rains and
high winds is indicated by its performance grade and
design pressure. The design pressure is a structural rating
only, while the performance grade also indicates that a
window has met the water resistance and air infiltration
standards for that grade (see Table 3-2 below).
[Click to enlarge any image, photo, or table]
The minimum recommended design pressure for residential
doors and windows is 15 psf. A design pressure of
15 means a window has been tested to withstand sustained
wind pressures of 22.5 psf, roughly equivalent to a 95-mph
wind, applied to either side of the window, simulating both
positive and negative wind pressures.
The test pressure is
always 150% of the rated design pressure to provide a
safety factor. To earn a performance grade of 15, a window
must also pass a water pressure test of 2.86 psf, which
simulates rainfall of 8 inches per hour with a wind speed
of 34 mph. In coastal areas or other areas prone to heavy
winds or hurricanes, higher grade windows are recommended
and may be required by code.
Industry Associations for Windows & Doors
American Architectural Manufacturers Association
Efficient Windows Collaborative
National Fenestration Rating Council (NFRC)
Sustainable by Design
Shareware calculators for sun angles, solar heat gain,
Window and Door Manufacturers Association
Reader question: what is the wind load [on windows or other structural components] at 200 mph
2/9.2014 lw said:
winds at 200 mph and what load ?
Reply: wind load calculation references
LW; several government PDFs as well as the Engineering Toolbox convert wind speeds to loading forces. For example a 50 mph wind would impose a load of 2.15 k N/M2. It's not linear so one needs to do the calculation.
There is a host of wind loading calculation approaches but the underlying concept is force x area or F = A x P.
Section 1620: " Design wind pressures for buildings and structures and elements therein shall be
determined for any height in accordance with the following formula:
P = Ce Cq qs Iw kzt (20-1)
The wind exposure type (given UBC in Section 16.16 & described just below) is used to determine the coefficient Ce according to Table 16-G.
Ce = combined height, exposure and gust factor coefficient (Table 16-G)
Cq = pressure coefficient (Table 16-H)
qs = wind stagnation pressure at 33 feet (Table 16-F)
Iw = importance factor (Table 16-K)
kzt = topographic factor
Note that this UBC 97 wind design code assumes (for the sake of low buildings perhaps) that the fastest wind speed is at 33 feet above the ground, not the actual peak sustained wind speed. That wind speed is given by a map included in the code. And the UBC Offers these Wind Exposure Levels:
EXPOSURE B has terrain with buildings, forest or surface irregularities, covering at least 20 percent of the ground level area extending 1 mile (1.61 km) or more from the site.
EXPOSURE C has terrain that is flat and generally open, extending 1/2 mile (.81km) or more from the site in any full quadrant.
EXPOSURE D represents the most severe exposure in areas with basic wind speeds of 80 miles per hour (mph) (129 km/h) or greater and has terrain that is flat and unobstructed facing large bodies of water over 1 mile (1.61km) or more in width relative to any quadrant of the building site. Exposure D extends inland from the shoreline 1/4 mile (.40km) or 10 times the building height, which ever is greater.
But it's worth understanding that wind damage resistance is more complex than just the effectsof loading force from wind itself. First the wind force will vary enormously on different building sides and even different building areas on the same side. Second, wind at high speeds picks up objects and hurls them with tremendous force -sufficient that we've seen a single sheet of paper cut into a tree trunk.
ASCE 7-02: Minimum Design Loads for Buildings and Other Structures. American Society of Civil Engineers, 2002.
Envirometrics, "MEETING THE IBC WIND LOADING STUDY REQUIREMENTS", [PDF], Envirometris, 4803 Freemont Ave., Seattle WA 98103, USA, Tel: 206-633-4456, retrieved 2/10/14 original source: www.envirometrics.com/abstracts/CFDwindloading.pdf
Kasperski, M., and H-J. Niemann. "The LRC (load-response-correlation)-method a general method of estimating unfavourable wind load distributions for linear and non-linear structural behaviour." Journal of Wind Engineering and Industrial Aerodynamics 43.1 (1992): 1753-1763.
Dyrbye, Claës, and Svend Ole Hansen. Wind loads on structures. John Wiley & Sons, 1996. [book]
Holmes, J. D., and R. J. Best. "An approach to the determination of wind load effects on low-rise buildings." Journal of Wind Engineering and Industrial Aerodynamics 7.3 (1981): 273-287.
International Building Code, 2003. International Code Council, Delmar Publishers.
Jorgensen, P., J. S. Christensen, and J. O. Tande. "Probabilistic load flow calculation using Monte Carlo techniques for distribution network with wind turbines." Harmonics and Quality of Power Proceedings, 1998. Proceedings. 8th International Conference On. Vol. 2. IEEE, 1998.
Kasperski, M. "Extreme wind load distributions for linear and nonlinear design." Engineering Structures 14.1 (1992): 27-34.
Leffler, R. E. "Calculation of wind drift in staggered-truss buildings." Engineering Journal, AISC 1 (1983): 1-28.
Pierre, LM St, et al. "The UWO contribution to the NIST aerodynamic database for wind loads on low buildings: Part 2. Comparison of data with wind load provisions." Journal of wind engineering and industrial aerodynamics 93.1 (2005): 31-59.
Rotach, Mathias. Estimation of the Wind Speed at an ‘Urban Reference Height’ from an observation at some other height. COST 715: European Cooperation in the Field of Scientific and Technical Research.
Smith, Stuart D. "Coefficients for sea surface wind stress, heat flux, and wind profiles as a function of wind speed and temperature." Journal of Geophysical Research: Oceans (1978–2012) 93.C12 (1988): 15467-15472.
Uniform Building Code, 1997. International Code Council.
WANG, Hai-chao, et al. "A joint iteration method for load flow calculation of power system containing unified wind farm and its application." Power System Technology 29.18 (2005): 59-62.
Array Solutions, "Wind Loads", Array Solutions, 2611 North Beltline Rd, Suite 109, Sunnyvale, TX, 75182 USA, Tel: 214 954 7140, Email: firstname.lastname@example.orgF. For a helpful discussion of approaches for calculating wind loading on features such as antannae, see arraysolutions.com/Products/windloads.htm
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