Making a Vinyl Window Impact Resistant
May 1, 2007
Consumer interest in impact windows and patio doors continues to grow. This trend—spurred on by changes to building codes and demands by insurers—has given manufacturers of all sizes the impetus to launch their own lines of impact products. But what should a vinyl window and door maker take into consideration before doing so?
For a window or door to be called an impact-resistant product and receive certification for a given sales area, it must first successfully pass impact and cycling test requirements, along with structural test procedures. Under the AAMA 506 labeling program, the product is tested in accordance with ASTM E 1886-02 or 05 and ASTM E 1996-02 or 05, as well as one of the three following structural standards: AAMA/NWWDA 101/I.S.2-97 or AAMA/WDMA 101/I.S.2/NAFS-02 or AAMA/WDMA/CSA 101/I.S.2/A440-05). In Florida, Dade and Broward Counties require products to pass the Miami-Dade Protocols (which include TAS 201, TAS 202 and TAS 203). These requirements are also recognized throughout Florida.
When a PVC extruder has its window systems tested for impact resistance, the test results are transferable to manufacturers. Choosing a system that’s already been tested for impact resistance can spare the window manufacturer considerably in laboratory fees, save time in what is often a lengthy product development cycle and clear up much technical uncertainty. For product certification purposes, however, it is required that the manufacturer comply with the extruder’s fabrication specifications. Any changes can compromise impact compliance. The instant a window differs from what was tested it must be re-tested.
If a window manufacturer chooses to make a product that has already been tested rather than develop its own, the choice of system and extruder made at the very start will determine the success or failure of its impact project. This decision will determine attainable production times, required training and the extent to which quality can be imposed consistently across the line. Making an informed decision requires close scrutiny of profile designers’ test reports. Anyone can choose products that performed well in tests, but attention should also be paid to how the product was manufactured by the extruder to arrive at these results. After all, the same specifications will have to be followed in the window manufacturer’s plant throughout the manufacturing process.
When choosing impact window and door systems, it is vital to fully understand the impact every aspect will have on the production, installation and marketing of the finished product. Generally speaking, the sturdier a standard window design is, the less it will need to be reinforced to meet impact standards. For instance, a system requiring up to three reinforcement parts for the interlock alone is not uncommon, whereas another system might perform equally well with only one interlock reinforcement. The amount of reinforcement required is certainly an issue manufacturers should pay close attention to when choosing a design. A window that performs well with a minimum of adjustments (e.g., hardware, glass, reinforcements, etc.) will be easier, quicker and less costly to manufacture.
DESIGN AND MANUFACTURING CONSIDERATIONS
When analyzing test reports, there are a number of key characteristics to bear in mind, besides the required design pressure:
- The simpler the basic test unit, the more flexibility the manufacturer will have. Accessories can be added afterwards without compromising test compliance. The opposite, however, is not true. If nailing fins were part of the window unit tested, for example, removal of these accessories would compromise the integrity of the unit and thus void the test results.
- The size of the tested specimen is also crucial—the larger the test-approved specimen, the fewer the dimensional restrictions on production units. The same goes for shapes, models and specimens being tested as single or mulled units.
- Glass thickness is usually proportional to window size (ASTM E1300). However, once an impact window has been test-approved, glass thickness must remain unchanged even in smaller sizes. With this in mind, one must pay attention to the glass thickness of the unit that was tested, as it can become a constraint to build smaller windows. A system tested with thinner glass gives fabricators the option to market more reasonably priced smaller units
- Laminated glass is required to prevent the glass from shattering upon impact and keeping the window intact, whether using single-pane glass or sealed units. Products with sealed units may have the laminated lite on either the inside or out. Occupants are better protected when the laminated glass is on the inside, as this prevents their home being showered with shattered glass if the outside layer is struck. It is therefore always best to look for products that have passed their tests with the laminate on the inside.
- Sealants tend to be silicone or urethane-based. It is important to know the individual characteristics of each formulation used in the tested product. Manufacturers should understand any differences in setting times and required equipment that may be required to produce their impact line.
It is in the manufacturers’ best interests to offer installers and consumers alternatives with an impact line. A number of factors can make the installation process much easier. It is important to choose a product that does not need to be dismantled for installation purposes. Some patio door models, for example, require two rows of screws, or are designed in such a way that the fixed sash cannot be installed before attaching the frame to the building. Given that some operations are quite simply more complicated to do onsite than at the factory, installers will always prefer a product with minimal complications.
There are also a number of things that increasingly savvy consumers are looking for when choosing an impact product:
- Easy to replace in the event of impact. Since impact window glass packages are embedded in sealant, replacing the glass alone in the event of glass breakage can be problematic. Choosing a model with operating sash only is therefore advantageous both logistically and economically. Allowing a sash to be replaced avoids having to deglaze or to replace the whole window. This alone justifies many fabricators’ preference for a double-hung window, even if a single-hung window is currently the most popular choice.
- Energy efficiency. Insulating glass impact units are much more energy efficient, a huge benefit given evolving building codes.
- Easy to maintain. As with regular windows, tilt-in sash or other configurations that allow the outside of the window to be washed from the inside are important to homeowners.
- Nice appearance. Homeowners want their impact-resistant windows to be both safe and attractive. The look of the window remains an important feature. Choosing a system that delivers the required performance with a subtle and discreet design is critical to the fabricator.
In conclusion, fabricators should invest time and effort in analyzing and choosing a manufacturer-friendly system upfront, considering appropriate consumer options for their market. With the right system, manufacturing impact windows will generally be no more complicated than standard windows. Offering the right products with proper certification can also build credibility for the manufacturer and facilitate product sales.
Caroline Dallaire is research and development manager and a shareholder in P.H. Tech Inc., Levis, PQ. A designer and extruder of vinyl window and door systems for the past 45 years, the company reports it was the first extruder with a vinyl window design to pass Miami Dade County large missile impact and cyclic pressure tests. More information is available at www.phtech.ca or by calling 800/463-4392.