Text excerpted from:
FENESTRATION MAY/JUNE 1993
Successful Vinyl Window Lines Depend on Good Product Design
Fabricators should understand a number of fundamentals when selecting
vinyl window extrusions
by Geoff Card
It's no secret that the best vinyl windows start with the manufacturing process and sound market research. Design engineers have learned some painful lessons by starting elsewhere. A litany of frustrating products dot the past (and present) and are recounted by manufacturers and extruders like horror stories around a campfire. Today's best window systems are comprehensive. They are designed thoughtfully and purposefully. A window design must address market requirements, efficient manufacturing, energy and building codes, installation/contractor needs, niche markets, price ranges, glazing and hardware options, composite window configurations, extrudability, marketing trends, as well as a host of regional homeowner preferences. Cream rises to the top. There are several advanced vinyl window companies which are successful in the renovation industry, and a few making good inroads into new construction. And it's no coincidence that all of their products share numerous advanced principles of product design. There is one fact that every vinyl window manufacturer is now facing low cost vinyl lineals mean absolutely nothing if they're accompanied by high labor costs during window assembly. This point is magnified several times for anyone making more than 15,000 units per year or considering automated or semi automated production lines. Standard window manufacturing times can range from between 30 minutes to 105 minutes. That can mean the difference of 3 to 20 windows per shop worker each day. With these differences, the low cost of a profile can quickly become inconsequential.
Manufacturing efficiency
Well designed window systems fall together and use an economical number of profiles which can be used interchangeably for different window types. This minimizes inventory, investment, and confusion. High-volume production plants require simple, efficient window assembly, and the minimum waste of extrusions which easily pass tolerance inspections. An extruder's tolerance clearances (the variance within critical profile shapes which can range between .3 mm and no limit) make a big difference in consistently achieving maximum plant production levels. Likewise, a minimum wall thickness of 1.5 mm makes all the difference in the world for plant workers welding together frames and sash. Many of today's most manufacturable windows use location-grooves to accommodate hardware. Self locating profiles provide fast, easy, "idiot-proof" manufacturing, and also strengthen the window. Additionally, the best window designs specify that screws travel through at least two walls of the multi-chamber profile to secure hardware and balances for long life and trouble free service. Barring experience, there is no easy way to assess manufacturing times simply by looking at profiles. However, talking to a non-competing company that makes the same or a similar product is a good start. The best assessment, of course, is to actually visit that manufacturer. In the case of automated lines, a fabricator should be certain that the extruder can provide verifiable information about automation from either an equipment supplier, or better yet, another automated manufacturer. The vinyl used today is light years advanced from the materials used only 10 years ago. The best vinyl profiles are high impact, ductile materials with generous amounts of expensive additives like acrylic impact modifiers and sophisticated stabilizers. These additives allow the vinyl to withstand weathering, as well as the demanding routine manufacturing processes like punching and cleaning.
Materials
Currently, about 20 extruders have AAMA certified lineals and submit their materials to tests for impact resistance, weathering, shrinkage, and color hold. This program is a good safeguard for all manufacturers concerned about consistent materials, ensuring that adequate quality control, verified by an independent third party validator, is exercised by the extruder. One of the bigger upcoming issues in material quality may concern regrind. Regrind, as its name implies, is vinyl scrap that is ground into pellets, then reused or sold to a scrap broker. Research indicates that vinyl can lose as much as 15 percent of its performance characteristics each time it is heat processed. While small amounts of an extruder's own regrind has little impact on product performance, large amount (or worse, regrind from a broker) can be very risky for both the extruder and the manufacturer. Ideally, major components that are exposed to weathering should be extruded directly from virgin vinyl powder to maximize the product's performance characteristics. This issue may someday prove to be as volatile to extruders as the R- wars or U- value arguments now facing the window industry. The most important point here is that regrind of unknown origin should not be used in any profile.
Multi chamber profiles
Multi chamber designs of advanced profiles have empowered vinyl windows with a strength, energy efficiency, and performance that would have seemed miraculous 20 years ago. The best window profiles use at least two and preferably three chambers between their interior and exterior faces. The effect of multi-chambers on strength is well documented. Typical welded profiles provide 9 to 20 inches of weld seams, and window designs exist with as much as 25 inches of frame and 14 inches of sash weld seam. The result is a virtually indestructible uni body window that can with stand tremendous pressures without reinforcement of welded corners. Vinyl has an expansion/contraction coefficient 2.8 times greater than aluminum. Profile and multi chamber design also plays a major role in controlling thermal movement. Engineers now design their profiles to dissipate the effects of extreme heat and cold. Although the process isn't easy to understand, essentially, the multi chambers of vinyl profiles dissipate the effects of outside temperature change, while the internal walls hold the shape of the profile in place. The result is a low practical co-efficient of expansion. The best multi chamber profiles also act as efficient drain- age routes. In any window some moisture formation is inevitable. The question is how to get rid of it. Some windows don't allow for moisture or use simple weep holes. Well designed vinyl profiles are pressure equalized (using the rain screen principle), have separate chambers for metal reinforcement, and direct moisture away from screws, hardware, and window seals for improved glass life. Energy legislation will completely transform the window industry by the end of the decade. States like Florida, California, Minnesota, Oregon, Washington, Georgia, New York, and Idaho have already proposed energy mandates for building products. Although glass plays the largest role in determining U-values, window frames comprise a substantial 20 to 25 percent of a window's total surface area. Multi chamber profiles are essential for energy savings. They improve thermal performance by blocking energy transfer between the dead-air chambers. A very useful gauge of a window frame's insulating quality is the condensation resistance factor. CRFs measure a frame's relative warmth, and many design experts view them as a useful overall indicator of a window's composition. Window industry CRFs are typically between 49 and 77, with high-quality vinyl windows falling into the mid-60 range and above.
Versatility
The need for different window styles and appearances vary with each region of the country and types of applications. Good window designs give fabricators a wide range of different window types within a limited number of required profiles. The new frontier for vinyl windows is new construction. The new construction industry is an entirely different world than the renovation industry in which vinyl is firmly entrenched. New construction has different terminology, different distribution, different manufacturing, and significantly, different installation preferences that vary between regions. Farsighted window designers are quickly becoming aware of this. Options like aluminum and integral vinyl nailing fins and an assortment of clip on supplementals are gaining tremendous importance. When a salesperson presents a window system to a builder, labor saving features like sheet rock returns can greatly influence the purchase. Vinyl window brick molds, stucco or wood returns, and snap on supplementals make a difference in project bids, which can involve thousands of windows. Glazing options are a commonly overlooked feature in window systems. By designing glazing beads that allow for a wide range of glazing options, vinyl extruders enable fabricators to tap into good better best sales, as well as many niche markets. On site glazing or replacement can also be a weighty issue with some contractors. Internal glazing beads give them this option while enhancing a home's overall security. Structural supplementals like mullions, transoms, and T- mullions used with or without aluminum reinforcement are another significant factor for many parts of the country. Regions like the West Coast require large windows to be mulled together, essentially forming window walls. Used in combination with T mullions to create distinct lites within an existing frame, these mullions make vinyl windows more versatile for the architectural and commercial markets as well. Other composite configurations, like bay/bow windows, comprise up to 85 percent of casement installations in some areas of the Northeast. Thus, the need for versatile window systems which use specialized mullion transom components are extremely important to window manufacturing companies. The tremendous changes taking place in the vinyl window industry place a renewed emphasis on technical-marketing research, real life testing and development, and plain common sense. A rising tide lifts all ships. With the advent of the Age of Custom Profiles, good designers will need to judiciously use successful, established design concepts, for the good of the entire industry, and window manufacturers will need to become educated as to what a good design encompasses. The successful vinyl windows of today are based on sound design principles. When combined with new innovations for tapping into wider markets, these same fundamentals will continue to drive the products forward in quality and acceptance.
Geoff Card
is vice president national technical marketing for Spectus Systems, a Winnebago, IL, company which designs and extrudes vinyl window profiles. With nearly 29 years of experience in the industry, he has served as chairman of the British Plastics Federation Windows Group and represented the UK government on European window standards. He now works closely with several American associations, including the California Association of Window, Manufacturers, with particular emphasis on energy performance issues.
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Multi-chamber profiles provide vinyl windows with increased strength, energy efficiency, and performance versus single-chamber designs, with the best window profiles use at least two and preferably three chambers between their interior and exterior.
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Versatility in window systems can be important to fabricators. Snap on components, such as interlocks, allow a variety of windows to be produced while minimizing inventory requirements. Other snap on components, such as this supplemental return, can be used to make vinyl windows more attractive to builders.
FENESTRATION MAY/JUNE 1993 Vol 6, No. 5
ASHLEE Publishing
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New York, NY 10017
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