The debate has been raging not only in this industry but also in textiles, food packaging, toys and others: Can UPVC (Unplasticized Poly Vinyl Chloride or rigid PVC) be considered a "green" product?
Like in so many debates the answer is "yes and no." It depends what you are comparing to and how "green" is defined. Lets start with an important upfront definition: In this debate "green" will be used to describe the lesser amount of environmental impact over the lifetime of the product. Using this definition let's look at three distinct areas: The raw materials used to make windows, the production process, and the characteristics/maintenance over life of windows.
1) Raw materials: In the window industry today you have basically four types of frames/sashes (let's exclude glass since it will be same for all four): UPVC, Wood, Aluminum, and Wood covered with Aluminum. There are other metal claddings and profile metals such as bronze and steel but both are disqualified because of their energy properties from this discussion. In Europe steel windows are not even allowed to be used in residential construction. UPVC is manufactured from crude oil and rock salt through a serious of stages. The big difference between PVC and UPVC is that the latter does not contain phthalates, the softening acids that easily leak into the environment as the plastic polymer disintegrates over time. As a result UPVC does not gas out toxic substances. While crude oil is a non-renewable fossil fuel, the main ingredient rock salt is available in virtually unlimited amounts.
Wood as the substrate for window frames and sashes is still the most frequently used. Depending on the type of wood (pine, fur, meranti, mahogany) used, the raw material could be from sustainable sources or not. Assuming that most large manufacturers have now fully converted to sustainable sources, the wood has to be transported from the harvest location to the factories, usually a large distance especially in the case of tropical wood species.
Aluminum is the least "green" raw material because bauxite is a non-renewable mineral which requires large amounts of energy to be converted to the end product.
2) The production process: UPVC windows are manufactured from standard profiles. In the manufacturing process these profiles are cut and welded under strict environmental guidelines. For coloring, either colored profiles are used (the color is in the polymer) or, more frequently, a thin PVC layer of color laminate is melted and pressed onto the profiles. Wood window profiles are made by laminating several layers of wood together in a way that reduces warping. The lamination process involves water soluble glue. The these profiles are then run through routers, saws, and joiners. After the joints are glued, the window frames and sashes go through a painting and sanding process. While all these manufacturing processes have been optimized to meet environmental standards, wood requires far more extensive processing and application of glues and paints than UPVC. Aluminum windows are processed very similarly to UPVC, with profiles being cut and joined either through welds or glue. All aluminum windows are powder coated for color. In the comparison UPVC windows are produced with the least environmental impact.
3) The characteristics and maintenance over life: UPVC windows are virtually maintenance free. Colors stay on the profiles for a life expectancy from between twenty and fifty years. Wood windows require periodic re-finishing depending on exposure. Typically, wood windows are painted every three to five years. The life expectancy of a wood window is between seven and fifteen years. Aluminum windows are powder coated and, while the colors fade over time depending on exposure, these windows do not require maintenance. However, one of the biggest disadvantages of aluminum versus UPVC is that in a salt air environment aluminum oxidizes, reducing the life expectancy to ten years. In comparison, UPVC windows require less maintenance and have a higher life expectancy than the other types of windows. The real disadvantage of UPVC is the issue of end-of-life disposal. While European manufacturers are forced by their governments to provide collection and recycling services, here in the United States there is little control over the disposal of vinyl products. While UPVC is fully recyclable and the percentage of recycling is increasing year by year, the lacking regulation of the industry does put a damper on an otherwise "green" product with the least environmental impact from raw material, manufacturing to life expectancy and maintenance.