Selecting a window system for use in new or renovated commercial and institutional buildings has typically centered on aluminum, steel, aluminum-clad wood, or vinyl windows. In the last five years, however, another choice has gained popularity for a lot of good reasons. Fiberglass window systems are being specified and installed more and more in retail facilities, offices, schools, colleges, condominiums, apartments and many other buildings that commonly have relied only on metal window systems in the past. To understand this emerging trend, let's begin by looking at some of the basics of fiberglass window technology.
Natural Materials Blended with Technology
While the term "fiberglass" is used as if it were a single material, it actually is a composite that consists of glass fibers and a resin that binds those fibers together. Glass fiber, made from natural silica and other materials, has a surprisingly high tensile strength. This characteristic has been demonstrated in many building product applications showing it to act like the equivalent of many reinforcing bars in a concrete mix. The resin that is introduced acts like the concrete itself that forms and holds everything together with the added benefit of performing well in compression. Combined together, the glass fibers and resin create a material that is stronger than either of them individually and provides strength in both compression and tension.
A key point to remember is the type of resin used to make the composite fiberglass material. In general, all resins can be put in one of two categories: thermoplastic or thermoset. In simple terms, thermoplastic materials can be re-melted while thermosets cannot. Most commonly used plastics are made from thermoplastic resin including vinyl windows which are made from PVC, a thermoplastic resin. These materials soften as they are warmed and if heated high enough will melt. This is how plastics are recycled. Thermoset materials, in contrast, undergo an irreversible chemical reaction. Often initiated by heat, once this chemical reaction has occurred, thermosets do not soften or melt as they are reheated. Fiberglass composite windows are made using thermoset resin. As a result, fiberglass composite windows can be used in hot climates and can be painted dark colors, even in high sun exposure applications. If vinyl windows are used in these applications, it is possible for the vinyl to soften, causing the material to sag or warp. The term, "vinyl smile," is sometimes used in the industry to describe this phenomenon. This is most often seen when the head of a large span sags after becoming too hot.
The process of making fiberglass window frames is also different from making aluminum or vinyl frames where the process of extrusion is used, which means the material is pushed through a die to shape. Instead, fiberglass frames rely on a process called pultrusion, in which thousands of glass fibers (called rovings) are pulled through a steel die. (See Figure 1.)The resin and fiber are given shape as they are pulled through the die which is heated to initiate the resin's cure process. The hardened result is then cut to the desired length and prepared for finishing. A paint finish is applied to the fiberglass to provide the final coloring and UV resistance to protect the finished product from sun exposure. Â In testing performed in accordance with the American Society of Testing and Materials (ASTM) testing standards, fiberglass composites manufactured in this manner consistently display superior performance in strength, ability to withstand extreme heat and cold, and resistance to dents and scratches.
There are several characteristics of fiberglass composite windows that have contributed to their increased use in commercial and institutional buildings, including:
- Durability. In addition to its great strength, certain factory-applied finishes render fiberglass composite virtually indestructible and long lasting. Further, it will not corrode or rot.
- Impact resistance. (See Figure 2.) Fiberglass composite withstands major impacts without deformation, especially in cold weather. Impact resistance is particularly important on the job site during installation, when dents and damage may inadvertently occur.
- Hot and cold performance.Fiberglass composite can handle a wide range of temperature extremes, withstanding heat up to 200 degrees Fahrenheit, and cold to -40 degrees Fahrenheit.
- Thermal expansion. (See Figure 3.) Fiberglass composite has a very low coefficient of expansion which is very similar to glass. As a result, it moves very little as the weather changes, resulting in less stress on the installation, seals, and glazing of the window. In addition, since fiberglass composite is very heat tolerant, it can be painted dark colors without concern for heat deformation.
- Energy efficiency. (See Figure 4a & b.) Fiberglass composites rank high because of their inherently low heat conductivity. Further, they are commonly offered with added insulation inside the cavities of the frames and sash, boosting the overall thermal resistance value of the unit. As a result, the material also has a higher condensation resistance than other materials. As shown in Figure 4a, fiberglass window units rate 2.4 times better than aluminum with a thermal break and even better compared to aluminum frames without a thermal break. As a result, they also provide superior thermal comfort to those seated near windows.
- Sustainability. Fiberglass composites consume less embodied energy to produce when compared to aluminum and vinyl.
- High performance. The finished units provide excellent resistance to air and water infiltration particularly in high winds making them very appropriate for coastal applications. They also serve as effective sound barriers between outdoor and indoor spaces.
- Finish. The final factory applied finish coat is typically scratch resistant, low-maintenance, and resists chalking and fading-even in dark colors.
- Installation, operation and maintenance. Fiberglass composite units typically arrive on-site pre-assembled and pre-finished, which makes them easy to install, and low maintenance over the long term.
The net result of all of these characteristics is that fiberglass composite windows offer an advanced alternative for commercial buildings of all types. They provide exceptional energy efficiency and durability even in extreme weather conditions while combining the beauty of durable finishes with the outstanding performance commercial projects demand.
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What are the cost implications of Using this Material?
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