Low thermal conductivity

Pultruded fiberglass has a low coefficient of thermal conductivity (2.08 BTU/ft2/hr/oF) similar to other low conductivity materials such as PVC and wood. Because pultruded profiles can be made very thin (0.070 inch) they create a narrow heat path for thermal bridging that results in excellent thermal performance when the overall window is evaluated using the analytical aids and simulation programs available to the industry.

Strength

The tensile and flexural strength characteristics of pultrusions permit a stiffness in window designs similar to conventional metals without the thermal trade trade offs. Metal reinforcement is typically not required. This property is illustrated in a conversion of a PVC design to pultruded fiberglass by Spilka of Norway, a leading European supplier of windows hardware systems. In this case it was important to maintain only the external geometry of the structurally-reinforced PVC profiles - not the internal configuration.

Resistance to moisture

Pultruded fiberglass is virtually impervious to moisture (it has a moisture migration rate of 0.17 percent). Susceptibility to moisture is what causes some other framing materials to rot, warp, crack, or twist. With a stable substrate, coatings can be easily applied to pultrusion to provide freedom of design in terms of color. With a high heat distortion temperature pultrusion, is much like aluminum in its receptivity to sophisticated coatings technology. Blomberg Window Systems of Sacramento, which pioneered the all-fiberglass windows in California, offers a factory-applied, baked-enamel finish in the deep rich colors often preferred on the West Coast and in the temperature extremes of desert climates.

Stability over temperature extremes

Pultrusion, like glass, has a very low coefficient of thermal expansion/contraction (3.8 x 106 in/in oF). It does not distort in the extreme hot or cold temperatures to which window frames are subjected. Window frames of pultrusion hold their original shape, are impervious to temperature changes, and maintain their initial air infiltration rates. Another benefit of this property is that fiberglass can be laminated with vinyl woodgrains, a technique employed by Fibertec of Toronto.

Corrosion Resistance

Pultruded fiberglass is unaffected by the chemicals, salt air,and acid rain which affect window frames in harsh environments. Fiberglass does not corrode. Other innovative applications that capitalize on specific properties of pultrusion include windowsills (moisture resistance), door thresholds (thermal and structural properties), and skylight and roof windows (low coefficient of expansion). AltaTherm Industries of Edmonton has developed an innovative pultruded door frame for an entrance system that has found a ready market in Japan, as well as North America.

Energy performance

High thermal performance by FRP lineals has resulted in fiberglass windows achieving unsurpassed ratings under the Canadian Energy Rating (ER) system, developed by the Canadian Standards Association. The ER system provides a method for evaluating the total performance of a window. It takes into account the effects of solar gains, air leakage, and glazing and frame heat loss over the winter season. This single ER number allows buyers to compare the energy performance of similar window types on a common basis.

The unit measure of the ER number is watts per square meter. A positive ER number indicates that the window is an overall contributor of energy over the heating season meaning that the heat loss is actually less than the solar gain.

The ER numbers for two types of typical residential fiberglass frame windows, a fixture or picture type and a casement type are presented in Table 1 on this page. For each type, results for three windows are listed,

Window	Size (mm)	ER
Fixed, double-lite, 1 Low-E, argon, insul spacer	1220 x 1220	+5
Fixed,triple-lite,clear, metal spacer	1220 x 1220	+2
Fixed,triple-lite,2 low-E,2 argon,insul	1220 x 1220	+11
Operable,double-lite,1 low-E,argon,insul	600 x 1220	-4
Operable,triple-lite,clear,metal spacer	600 x 1220	-8
Operable,triple-lite,2 low-E,2 argon,insul	600 x 1220	+2

including a high-performance double-lite window incorporating a low-emissivity coating and argon gas fill,a standard triple-lite window, and a high performance triple-lite unit with two low-emissivity coatings and two argon gas fills. As a reference point, it should be noted that the current Ontario Building Code requires that the minimum ER levels for windows installed in electrically heated homes be 0 for fixed windows and-13 for operable windows. The ER numbers listed in Table 1 are significantly better than these minimum performance levels.

Fenestration industry participants face the challenge of providing aesthetically-pleasing , energy-efficient, and competitively-priced products to a discerning market at a time when there are concerns both with supply and volatile price movements with some traditional materials. It has become clear that the quality window of the future will not be monolithic - be it wood, aluminum, PVC, fiberglass, or some other material. Rather, tomorrow's designs will incorporate a variety of materials based on their physical and economic properties, their availability - and increasingly - by the perception of consumers about the material's environmental impact.

Pultruded fiberglass is emerging as a candidate to participate in those leading edge designs. Progressive window manufacturers and other authorities have recognized the potential of pultrusion and are often exuberant in describing the potential of pultruded fiberglass in fenestration applications.

A window industry leader has stated, " (…pultruded fiberglass) signifies the next wave of technology to hit the building products industry and will redefine the performance standards for windows."

In announcing the features and benefits of its new skylight, another industry leader's ad proclaimed, "…and the sash is made from a single profile pultrusion of a polymer so strong, durable, and corrosion resistant, it's used along seacoasts as a substitute for structural steel."

In this day of re-engineering, continuous improvement,empowerment, and other popular cures for business ailments, we are often told that innovators must learn to think "outside the box". Not so in the window game. Innovative manufacturers are looking at the box - not outside it. And increasingly pultruded fiberglass is becoming part of the solution.