Fiberglass Windows

Hello again this is John Whalen and in this article I wanted to explain a little about the fiberglass product and its use in window construction. Fiberglass windows have been on the market for several decades, though most people have only recently heard of them.  The process for making the lineals that the fiberglass windows use in their construction is called pultrusion.  This method is where fiber and resin are pulled through a heated die to make the frame parts of the window.  The material is strong, durable, has excellent insulating properties and can be painted either by the factory or the consumer.  Typically, these windows are available in double-hung, slider, picture window and casement series.  The construction method for these windows is generally gusset mechanically fastened screwed corners, with either a wrap around glazing or a snap in glazing for the glass.   With the current technologies used in fiberglass window construction, special shape geometric windows such as circle-top, eyebrow and quarter round windows are unavailable.  These windows are generally made from vinyl extrusions and mulled to the fiberglass windows.

Pros of the window are:

  • fiberglass is a very strong product and it can be used in some large applications
  • it is paint-able
  • has good BTU ratings
  • last for years

Cons of the window are:

  • the material is extremely heavy making installation more difficult
  • corner seams are mechanically fastened making them more likely to leak
  • fiberglass is difficult to drill through and requires a great deal of shimming
  • the pultrusions are hard and hollow making total insulating around the frame very difficult
  • attaching hardware such as locks and crank mechanisms are problematic because screws work loose as they don't thread into the fiberglass very well
  • surfaces are painted and may require maintenance in the future
  • geometric shapes are unavailable (they are generally made of vinyl)
  • it's a bit pricey

My thoughts...

For flexibility in color, fiberglass windows are a great choice and for large sized applications, they can solve problems.  While we do sell the product, from an installation perspective , it is very labor intensive; you'd better know exactly what you're doing, or you could come across some real problems!  From a construction viewpoint, the product is difficult to work with. In its construction, fiberglass windows require screw-blocks to attach hardware properly. All-in-all, the product needs more development to be an efficient choice.  However, for the consumers that prefer fiberglass, we do offer what I consider one of the best made to date.  Despite its strength and durability, I give this product a B or B- rating.