What are Glass Block Windows?

Elizabeth West
Elizabeth West
Silicone sealant, which can be used to put glass block windows together.
Silicone sealant, which can be used to put glass block windows together.

Glass blocks fastened together in a frame make attractive glass block windows, which allow light into a dwelling and also maintain privacy. They were originally used in early twentieth century factories to let in natural light before the widespread advent of electrical lighting. Glass block windows come prefabricated, or they can be custom made on site. They can be used in bathrooms, stairwells, sidelights and even as whole interior walls that are non-load-bearing. These blocks are available both clear and colored, with patterns and even etchings, and in acrylic as well as traditional glass.

Prefabricated glass block windows arrive in a vinyl frame that is fitted right into the opening. Their thickness and sturdy construction make them very difficult to break, ensuring security for ground level and basement windows. Whether custom or prefabricated, glass block windows are put together with either mortar, grout, or silicone sealant and then mortared into the frame. Silicon has the advantage of clarity, so there isn't a noticeable grout line between blocks.

Glass block windows are a popular choice in bathrooms. In some older homes, the bathtub is installed on the outside wall and the window is situated above the tub. Water damage is a problem in bathrooms, but changing a wood frame window out for a glass block one solves the problem as it is impervious. It also provides some insulation so the tub won't be too cold. Although a vent fan helps with humidity, the glass block can incorporate a small opening to release moisture and let in fresh air.

The blocks can also be used to construct shower surrounds in homes, partition walls in commercial buildings, and even large portions of outside walls. They are not load-bearing and won't work for an entire outside wall. Companies that make the glass blocks often provide installation services as well, assisting contractors on large commercial projects. Glass block windows are great insulators, keeping energy costs down, which can be considerable in a large building. The maximum size is 144 square feet (13.3780 square m); for anything larger, reinforcements need to be incorporated to handle wind pressure loads.

Acrylic block is lighter and safer than glass, and admits just as much light. Thinner blocks can be made into fully operable casements, sliders, and even single hung windows. One disadvantage to acrylic is that it scratches more easily than glass with use of some household cleaning agents. A soft cloth with a non-abrasive cleaner should be sufficient to maintain the window. Whether traditional or acrylic, glass block windows are a beautiful architectural elements and a good choice for saving energy in nearly any home or business.

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    • Silicone sealant, which can be used to put glass block windows together.
      Silicone sealant, which can be used to put glass block windows together.