Approximately 80 percent of its weight is PVC resin, with the remaining 20 percent being composed of other ingredients that establish color, opacity, gloss, impact resistance, flexibility, and durability. It is the most commonly installed exterior cladding for residential construction in the United States and Canada. There is controversy concerning the use of this product within the building industry, especially within the growing green building industry, due to environmental concerns in the processing, manufacturing, and disposal of the product.
This original process made it difficult to produce and install a consistent, quality product. Beginning in the 1970s, a transformation of the product began, with the industry engineering formulation changes. These changes affected the product's production speed, impact resistance, and range of colors.
Today, vinyl siding is manufactured by coextrusion. Two layers of PVC are laid down in a continuous extrusion process; the top layer is weatherable capstock, which comprises about a third of the siding thickness. This capstock includes about 10% titanium dioxide, which is a pigment and provides resistance to breakdown from UV light. Vinyl siding, like paint, will inevitably fade over time, but the fade rate is somewhat slower with vinyl, and in any house cladding (vinyl, paint or others) the intensity of the color is in direct correlation to the rate of fade. For example, two currently popular colors are "barn red" and "clay". In reaction to sunlight, the barn red will fade faster than the very neutral clay color whether paint, vinyl siding or other composition. The lower layer, known as substrate, is typically about 15% ground limestone (which is largely calcium carbonate). The limestone reduces cost, and also balances the titanium dioxide, keeping both extrusion streams equally fluid during manufacturing. A small quantity of tin mercaptan or butadiene is added as a stabilizer to chemically tie up any hydrochloric acid that is released into the PVC material as the siding ages. Lubricants are also added to aid in the manufacturing process.
Chemical formulas can also vary somewhat from manufacturer to manufacturer which can impact life expectancy. Most important is a UV coating that most major manufacturers apply to the surface of the product that filters out UV spectral light from the sun which would otherwise degrade the PVC more quickly. As a rough general rule, the higher the grade (and price) of the siding, the more resistant it is to fading (intensity of the color being taken into consideration, as mentioned above).
Vinyl siding is manufactured with its own partial fastening or locking system that is coupled with nails that 'loose' fasten the product to the exterior wall. This locking system can be either a rolled or an extruded lock depending on the manufacturing process, either of which having its own design considerations. This locking system has a bottom lock which locks into either a start piece or onto the top lock of the panel below. The top lock is then 'loose' nailed to hold the panel to the wall. This 'loose' nailing allows for float which is created by expansion and contraction from varying temperature and weather conditions. With well designed siding, and proper 'loose nailing' installation, the siding can easily expand up, down, in and out, and left and right without restriction. Vinyl siding, by it's nature, will tend to expand and contract more with temperature extremes than any other common type of cladding.
Vinyl siding, like natural wood siding, is flammable. However, because of its thin profile, vinyl siding may be more likely to ignite due to exterior fire; for example, the National Institute of Standards and Technology found that, in tests involving vinyl clad structures in close proximity, fire was observed to spread between two vinyl-clad test structures, located six feet apart, in less than five minutes. Additionally, vinyl siding can release toxic fumes when burning, particularly dioxins. This is not only an environmental concern, but the fumes can be dangerous to firefighters and bystanders, and the toxic fumes released may increase the likelihood of fatality from smoke inhalation for anyone trapped in the burning structure.
In Section 2.1.5, of the NAHB Model Green Home Building Guidelines, points are awarded for using building materials that require no additional finish resources to complete on-site application. [NAHB Research Center, Inc. NAHB Model Green Home Building Guidelines. Version 1. Part 1. Section 2. Resource Efficiency. 2.1.5. December 13, 2004.]. Because vinyl siding requires no paint, stain, or caulk in its installation, it meets this NAHB requirement.
The PVC used in vinyl siding used to be produced in open vats, until 1971, when a rare cancer of the liver, angiosarcoma, was traced to vinyl chloride exposure among PVC workers, and strict workplace exposure limits were established by the Occupational Safety and Health Administration (OSHA). These changes required all vats to be tightly sealed, which led to greater capital costs and a concentration of the number of producers.