Fortified For Safer Living

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1 Fortified For Safer Living Module 5: Windborne Debris and Opening Protection In this module we re going to look at windborne debris. It s one of the issues that comes up in situations with high winds. Most windows are broken by flying debris. So the issue of windborne debris is something that has gained much more attention in the last 20 years, even though it s something that s certainly been observed for decades in the aftermath of hurricanes in particular. In the Fortified program windborne debris issues are pretty clear cut. We are requiring opening protection on all windows and doors to protect them from windborne debris impacts. What we will spend some time talking about is some of the products and the types of approvals that are required. The Windborne Debris Region In the Fortified program we actually extend the windborne debris region. The code defines windborne debris regions as within a mile of the coast where the basic wind speed is 110 miles or greater. In the Fortified program, we have extended protection by reducing that basic wind speed to 100 mile an hour or greater. Since the Fortified for Safer Living Program adds 20 miles an hour to the basic wind speed to arrive at the design wind speed, anywhere the design wind speed is 120 miles an hour or greater, opening protection is required. Openings and Opening Protection In terms of the definition of openings, openings are basically holes in the building envelope, which when opened (say, when glass is broken), create an entry for random pressure to enter into the building. Typically, we re talking about windows, skylights, sliding glass doors, entry doors, and garage doors any glass, other than impact-resistant glass, which receives positive pressure. One way you can handle the threat of debris impact is by using impactresistant glass. Otherwise, you re going to have to protect the glass, and glass that needs protection is considered by ASCE-7 as an opening. As mentioned in one of the earlier modules, what we re looking at in terms of opening protection for residential construction is resistance to the impact of a 9-pound 2x4 on the opening at 34 miles an hour. Now this covers a range of things. The 2x4 is representative of a lot of different 2008 IBHS or its affiliates, All Rights Reserved Module 5, Page 1

2 kinds of debris that might be flying around in a storm. It doesn t mean that you re looking at protection just from this particular missile, but you re setting a performance requirement that is consistent across the board so that you can compare one material and one product with another. Impact resistance standards. Basically, there are standards that have been set, and some of them are listed here in the chart below. SSTD-12 was one of the first standards for establishing impact resistance. Miami Dade and the Florida building code TAS 201, 202, and 203 actually predated that methodology, and predated SSTD-10 a little bit. But SSTD 10 was the standard building code approach for impact resistance, and it was designed so that anything that passed the Miami Dade protocols would automatically pass the standard building code protocols. But it doesn t necessarily work the other way around. Then more recently, the American Society of Testing and Materials, ASTM, had a committee that established more of a national consensus standard on debris impact protection, and that is expressed in terms of E1886 and E1996. E1886 gives you the test method, and E1996 gives you some of the performance requirements if the code you re using doesn t give you its own definition. Don t get confused by the fact that there are essentially three different standards the SSTD 12, the ASTM 1886 and 1996, and the Miami Dade Florida building code. Products need to meet one of those test standards. But contained within the test standards are three components to the standard: an impact test, a pressure test, and then what s called a pressure cycling test. I m going to cover this a little bit more in the future, but there are three components to any one of the tests. And products must be tested and approved, key word there being approved, for use in accordance with one of those standards. Types of Opening Protection The Fortified program requires opening protection or impact rating of all windows and doors in hurricane-prone regions, and those are defined as areas along the Atlantic and Gulf Coast where the design must be to the ASCE-7 (that is, greater than 110 miles an hour) or the Fortified design and wind speed would be greater than 120 miles an hour. In terms of options for protection, you can have a have a pressure- and impact-rated door or window, and typically, if it s a window with glass that s impact-rated, then it s going to have a fairly thick laminate in between the pieces of glass. So it s like the impact glass that you find on a windshield but actually with a much thicker interlayer. And it can take the impact of 2008 IBHS or its affiliates, All Rights Reserved Module 5, Page 2

3 that 2x4: The glass will break, but the membrane that s represented by the inner layer will stay in place and keep the wind and water out at least under that level of impact. The other option is to have a cover some sort of shutter or protective device that goes over the opening and provides protection for the opening so it won t be breached. In some cases, some of the standards allow for the glass behind the covering to break or even for a small opening or a hole in that protective covering, but the covering can t allow a big enough hole to be created to pressurize the building. We re going to cover some products that are impact-rated, but you can use combinations of protection types. You can use impact-rated windows and doors in some parts of the building and any one of the approved shutter systems in other parts of the building. Certain products work better for certain locations, so combinations are acceptable. And in the past, we ve had people struggle with trying to use all of one kind of shutter product, for example, when in fact you don t need to do that. So we ll talk about some of the different kinds of products and then how the application of those products can be based on what the individual product is good for. We have found that because of curb appeal and wanting to have something attractive on the face of their house, some people may go to impactresistant windows on the street side but use a much less expensive product, some sort of a shutter system, on the other faces. One requirement that Fortified does include is that upper level openings must be accessible from a balcony or some other structure, or you must have a permanent protective system that can be operated and put in place from the interior of the building. We re trying to prevent people from going up on ladders just before a storm to put up shutters on the second and third floors. We re referring to an operable shutter system. So if there s a fixed window on a second level, there s going to have to be either impact-rated glass or a motorized protection device that can be operated from inside. The number of different products then becomes limited. You have to be careful when looking at those upper floors and ensure that the windows (if they re operational) can be opened, such as with a double-hung or a single-hung window or a horizontal slider. Then you can open that window, reach out, and close the shutter system. But a fixed window, an awning window, or a casement window those don t work. Code-Allowed Minimum Protection The code has adopted an alternate requirement to keep costs down for 2008 IBHS or its affiliates, All Rights Reserved Module 5, Page 3

4 affordable housing. Primarily, 7/16-inch oriented strand board or plywood structural panels can be used as the protective system over openings. It doesn t currently have a product approval, but it s allowed by the code. The testing that has been done for the Florida building code and so forth does indicate that these panels will pass ASTM E1886 and 1996 because you can punch a hole in them with a 9-pound 2x4 at about 23, 24 miles an hour, and the hole won t open up. And as long as you ve got permanent anchors on and a well-anchored system, the plywood or the OSB will stay in place and resist the wind pressure loads. For remedial measures or for an existing home, we re recommending that you go up at least to the 5/8- inch plywood. We like plywood much better than OSB because typically the OSB has to be 30% thicker than plywood to have the same resistance. So plywood is a much more resilient and much more resistant material in terms of keeping debris out. Obviously we recommend the commercial systems that have a well-designed anchoring system as our optimum. Limitation of structural wood panels. It s important to note that there are some limitations on the use of structural wood panels. The maximum roof height is 33 feet. If we have a house up on piers and pilings, we may only be able to use structural wood panels on the first or second floor. So be aware that there are some limitations. One of the other limitations we also find is plywood typically finds itself built into some other project. Kids use it for skateboard ramps, etc., and we don t find an awful lot of people using structural panels. But it is something that s allowed by the code and we would encourage you to make sure that you install it correctly. The building in the photograph at left has plywood protecting its openings. You may notice the plywood is installed on the inside, but this is wrong. There are no approved products to use on the inside; the panels must be installed on the outside. Comparing the Standards The American Society of Testing and Materials ASTM E1886 is the one standard that is now widely referred to in the International Building Code, and that s the one that IBHS has adopted. However, 2008 IBHS or its affiliates, All Rights Reserved Module 5, Page 4

5 other standards may also be accepted; product that passes an old test with SSTD-12 or that has passed the Miami-Dade and Broward County standards will qualify. The ASTM E1886 test method allows for a range of missile sizes and so forth, but we re going to be dealing with missile D, which is the 9-pound 2x4, impacting at 34 miles an hour. There is also a small missile test that s recognized in ASTM E1886, and you will sometimes find some products, particularly window film, that may have passed the small missile test and so the manufacturers will say these products have met the E1886 test approval. But that is not missile D. And so you need to make sure that it passes the ASTM standard and it s the right missile. In some cases, the glass that s used to pass the test is 1/4-inch-thick glass or maybe 3/16-inch tempered glass. You ve got to be very careful and read the product approvals. The table below shows a relative comparison of the different standards. Location or Wind Speed () Test Standard SSTD 12 ASTM E1886/1996 Miami-Dade 110 < Site < lb ft long 40 fps = lb ft long 40 fps = < Site < 130 and >1 mi. from coast 8-lb ft long 40 fps = fps = fps = 34 Site fps = fps = 34 SSTD-12 is still being carried forward because it is a test method that was used for some of the older product approvals and those products are still being used. The ASTM E1886 is the one that s really taking over the broader range of products because it is the one being used by the International Building Code, while the Miami Dade product approvals are 2008 IBHS or its affiliates, All Rights Reserved Module 5, Page 5

6 valid for and required for anything built in Miami Dade and Broward Counties. You ll notice in the table above that they all come down to a 9-pound 2x4 at some point. With SSTD-10 there was a 9-pound 2x4 at 50 feet per second, 34 miles an hour. The 9-pound 2x4 is the middle one at 50 feet per second for wind speeds greater than 120 miles per hour in ASTM E1886. And obviously Miami Dade and Broward use it without grading things for different wind speeds. We mentioned earlier the use of a covering product that allows the glass to break behind the covering. There s no glass behind shutters (see lower row of photos below) when they re tested, but there s a penetration that is allowed by the ASTM, and you can shoot the missile through the shutter so long as the hole that s created doesn t allow the passage of a 3-inchdiameter sphere. For a product that s approved for use in Dade and Broward County, the high velocity hurricane zone here in Florida, they don t allow penetration. They don t allow a deflection that s going to be 2008 IBHS or its affiliates, All Rights Reserved Module 5, Page 6

7 enough to break the glass. So the major difference between the Miami Dade approval and the other approvals is penetration. The opening that can be created in a Miami Dade shutter is 1/16 of inch wide by 5 inches long. You can see that that s quite a bit different from allowing a 2x4 to actually pass through the shutter. But that is not a part of the test standard; it is part of the acceptance criteria IBHS or its affiliates, All Rights Reserved Module 5, Page 7