Question

What is the environmental footprint for manufacturing fiberglass windows? Is it safe for workers and the environment?

Asked by Kate Shackford
Bronx, NY

I have read that fiberglass windows are more energy efficient than aluminum.

Answer

Cynthia Phakos

Answered by Cynthia Phakos

Los Angeles, CA

Koffka Phakos Design

March 10, 2011

Fiberglass is made of polyester resin reinforced with glass fibers.

Though glass is quite brittle, when it is drawn into fibers its tensile strength increases enormously; and when combined with the resin, it makes for the strongest available construction material on an equal-weight basis

  • Once it has cured, it will not creep or deform over time.
  • It can accommodate higher wind loads with little deflection and can withstand extreme temperatures (-40°F to 350°F+) with little thermal expansion.
  • Also, as it is an inorganic material and chemically inert, it is not susceptible to rot or decay, mildew, insect damage, or UV degradation.
  • It has low embodied energy, and is safe to handle and dispose of.

Fiberglass windows have been used in Canada for as long as the States have been using vinyl. We are just now catching up with Canada, where their extreme winter weather conditions have caused them to develop a highly efficient window.

Worker safety

As far as the safety of the workers, the manufacturing process is automated and human exposure can be minimized. There are different methods of production, and the degree to which one operates the equipment varies.

I looked into Tecton Products in Fargo, North Dakota, and Roanoke, Virginia, which is one of the largest suppliers of fiberglass poltrusions and the supplier for Marvin’s Integrity Windows.

  • Tecton Products is an OSHA MACT (Occupational Safety and Health Association Maximum Achievable Controlled Technology) facility
  • And Tecton complies with the requirements of the 1990 Clean Air Act.

The input materials in themselves have hazardous implications, but when the resin is cured and bonded with the fiberglass, the resulting material is inert.

The material aspect of the windows can be better understood through the MSDS (Material Safety Data Sheet) for the product.

  • When you look at buying a particular brand, you should ask the manufacturer for their MSDS for the product.
  • In some cases, a manufacturer may include finishing techniques which may trigger other issues. Tecton, for example, has a patented acrylic finish which further protects the frame from extreme climates.

Environmental features of fiberglass

A negative environmental feature of fiberglass is its disposal.

  • As it can withstand seemingly all forces of nature, it therefore cannot degrade and must be considered a “monstrous hybrid.”
  • Aluminum can be recycled infinitely back into itself with little deterioration and so is a “cradle to cradle” material.

There are many environmental benefits of fiberglass windows over aluminum, with the key benefit their enhanced energy performance.

  • Thermal Conductance: Fiberglass has less thermal conductibility than aluminum (500 times less), and so a fiberglass window frame acts as good insulator.

  • Thermal Expansion: Fiberglass has almost zero thermal expansion. Fiberglass is essentially the same as glass itself, which means the frame and the glass work as a single unit with less movement which creates a tighter seal against weather. Glass has the lowest expansion and contraction rate of any window material used. Aluminum and its alloys have a relatively high coefficient of thermal expansion. For example, in structural calculations it is assumed that an unrestrained piece of aluminum 18 feet long will expand or contract ¼” in a 100 degree F temperature change.

  • Strength: Fiberglass is two times stronger than aluminum.

  • Durability: Fiberglass has almost zero thermal expansion rate and so is longer lasting.

  • Maintenance: Fiberglass is virtually maintenance-free and stays true to its form due to its strength. There is no need for sanding, painting, or staining, though it is a paintable surface. 

  • Durability: Fiberglass won't discolor, warp, rot, corrode, dent, or rust. It can withstand winds to 200 mph, does not absorb moisture and is not affected by UV exposure.

Environmental features of aluminum windows


The largest environmental impact with aluminum is its production process, which is energy intensive, and of the many window frame types has the highest value for NRE (non-renewable energy).

When first mined, the production of aluminum produces dangerous pollutants like carbon dioxide, acidic sulphyr dioxide and polyaromatic hydrocarbons, fluorine and dust.

However, aluminum is produced from an abundantly available ore, bauxite, and can be easily recycled without comprising its performance.

The Material Safety Data Sheet which Alcoa lists for Aluminum Extrusions and Anodized Aluminum Products (MSDS 509) has a dust exposure warning very similar to that for glass fiber.

  • More significant are the health effects from the mechanical process (e.g., cutting, grinding). Chronic overexposure can cause pulmonary fibrosis, secondary Parkinson’s disease, and reproductive harm in males.
  • The welding and melting process, with chronic overexposures, can also cause lung cancer.

Cold Climates

For your cold climate, you would be advised to get a frame that is better insulated. On this criteria, fiberglass windows perform better than aluminum.

  • Aluminum is a high thermal conductor and raises the U-factor of the window, so is not such a good insulator. (The lower the U-factor, the better the window insulates).
  • An aluminum frame will also cause condensation on the warm side of the window when the hot air meets the cool frame.
  • Finally, as there is more movement in the aluminum frame due to thermal expansion, you are apt to get more air leakage.

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