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Reply to: I agree with There's no substitute for research. Knowledge is power and an educated consumer will be a happy consumer, so I am going to address some of the points of your post. - design pressure - although the design pressure is important, it is an approximate measure of how much wind pressure the installed window (or shutter) can withstand without failure. Design Pressure is part of the three-part air, water, structural test that determines much about a window's overall performance. Air infiltration is the first phase, water penetration is next, and structural is the third part of the test. Windows are tested for air infiltration simulating a 25mph wind (1.56PSF pressure loading), and is independent of DP, while water infiltration and structural are based on the window design pressure. Water infiltration is tested at 15% and structural is tested at 150% of DP rating. A window with a DP30 is tested for water infiltration at 4.5psf (or 15% of 30psf) while a window with a DP40 is tested at 6psf (or 15% of 40psf), and so on. - There is a safety factor (which I believe is 30%) that actually REDUCES the performance of the window. In other words, when a window has a design pressure of 60psf, it has been tested at an additional 30% of that figure. 60psf x 30% = 78psf. Windows are structurally tested at 150% of the design pressure - a window with a rated design pressure of 60psf (~ 154mph) is tested for structural at 90psf (190mph). I have no idea what you are trying to suggest by "...actually REDUCES the performance of the window." ? In what way does a safety factor reduce the performance of anything? Also, since design pressure in psf is the square of the ratios of the wind-speed in mph, it’s relatively easy to calculate the equivalent windspeed performance (if so inclined) if you know the design pressure rating. - large missile impact - this test involves shooting a 9lb. 2x4 at the window (or shutter) in 3 difference places to see if the 2x4 will penetrate the product. Depending on the test, and the product being tested, there could also be only one or two impacts required. Impact windows are sacrificial products which means that they are DESIGNED to break but not allow the large missile to product a large hole to allow pressurization of the structure. That entire statement is ludicrous...Windows are made of glass, impact windows are made of glass. Hit glass hard enough and it's going to break. To suggest that the glass is "designed" to break as a "sacrificial" product is simply not the case. Contrary to what you might think, impact windows aren't "hurricane proof" or "shatterproof" and they will NOT survive a large missile impact during a storm. I am curious if you have verified data detailing exactly how many impact windows have been struck by flying 2x4's during a hurricane, since you are saying that they won't survive a large missile impact during a storm. Actually, it's quite possible to fabricate a laminated glass lite that won't break when impacted by a 2x4 at 50fps (or a lot faster - re: tornado impact resistant glass), but a viable product has to meet (at least) three simple objectives: 1) is it practical, 2) is it affordable, 3) is it effective. Unfortunately, fabricating laminated glass that won't break when impacted by the 2x4 might be effective, and may or may not be practical, but affordable is not in the picture unless you are willing to spend a great deal of money for them. They WILL break, they will allow shards of sharp glass to be hurled into the living space behind them and they will need to be replaced. Have you ever witnessed the test? If the impact is to a monolithic laminated glass (no IG), then there will be some spall (glass dust), but NO shards of sharp glass hurled into the living space...If the impact is to a laminated IGU and the laminated glass is the inside pane, then any broken glass from the outside non-laminated lite is stopped from entering the living space by the laminated glass - broken or not, NO shards of sharp glass hurled into the living space...if the laminated lite is to the exterior and the inner lite is the non laminated then it probably will break into large (and small) shards, and they will be dangerous, but saying that they are going to be hurled into the living space is overstated . The glass may break, but the laminated lite has absorbed most of the energy of the impact and that will limit the damage from raw broken glass to the interior. As a general rule, I much prefer impact windows with the laminated lite to the interior for that reason. Bottom line in any case, if you are in your home during a hurricane, standing in front of your windows (and I don't care what's protecting them) is not a really good idea). Breakage is not limited to hurricanes, either. Debris from lawn equipment and vandalism can also cause breakage. Debris from lawn equipment, and vandalism, and the odd baseball or golf ball can absolutely break windows...impact resistant or not. What's your point? Having laminated glass in the window may not prevent breakage, but it can help prevent injury. cyclic test - this test involves pressurizing the window (or shutter) 9200 times - 4600 with positive pressure and 4600 times with negative pressure. It starts at a low pressure and each pressure cycle is increased up to the predetermined design pressure. In the previous example, that would be 60psf. Actually 9000 cycles divided into eight different pressure ranges, four positive and four negative

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