Resource Depletion

The raw material reserves for silica sand are very large at present and are not expected to be exhausted. Quality control concerns in the production of glass fibre presently preclude the use of recycled fibre and waste is not recycled into the process though these options are being investigated.

In-plant waste resins for fibre glass are reused and re blended. The raw material reserves are based on the limits of petroleum products. The amount of petroleum is relatively small and contributes to a durable product that has a long life and energy efficiency not available from other products.

The polystyrene insulation is a petroleum product and, as mentioned above, has reserves based on the limits of petroleum. Again, a durable insulation is produced that has advantages in energy use reduction during the life of the window compared to other products.

Vinyl windows require a large quantity of poly vinyl chloride resins, which use petroleum as feed stock. Wood windows require clear heartwood for visible components placing a strain on old growth forests.

Emissions During Manufacture

Glass fibre production is said to be a closed process, with few emissions escaping to the environment. Resin manufacture is also said to be a closed process, with very few emissions to the environment. There is a chemical risk from the resins but it is less than that of PVC production. Expanded polystyrene is not produced in a closed process and some of the pentane blowing agent and other volatile compounds are able to escape.

The production of PVC releases petroleum byproduct to the atmosphere. the production of aluminum releases two fluorine gasses with potent greenhouse warning potential.

Ozone Depletion

There are no ozone-depleting chemicals used in the manufacture of fiberglass windows. The expanded polystyrene, however, uses pentane (approximately 7% by volume) as a blowing agent (a greenhouse gas).

Summary

The table below summarizes how the three window frame materials compare in addressing the eight environmental issues. Energy use was considered to be the most important environmental factor. From this analysis it was found that fiberglass windows have the lowest overall environmental impact. The energy efficiency and long life of fiberglass windows, significantly reduces then need for purchased energy, which means that their impacts on resource depletion and embodied energy is also limited. The high energy use and to a lesser extent the emissions during production of aluminum-clad wood and vinyl windows were the principle factors working against these products.