Insulated glass units consist of two or more panes of glass that are separated using a spacer to create a space of air between them. They are then sealed around the edges to prevent moisture from penetrating that space. This glass fabrication technique helps to minimize the transfer of hot or cold air, making it an energy-efficient window option for homes and businesses. Rest assured, all of our insulated glass is IGCC certified and goes through multiple inspections to ensure a quality and effective product.

We manufacture IGUs that are classified as “dual sealed.” The two seals are the primary and secondary. The primary seal is a poly-isobutylene material, also known as PIB or butyl. The secondary seal used will be either silicone or polyurethane. The size, shape, and make-up of the IGU will determine which type of secondary seal is used. Here are the guidelines that will determine which secondary seal will be used. Click here for more information.

Northwestern Glass Fab manufactures our custom insulated glass units daily in our facility. Our high-quality units carry a ten-year warranty for seal failure, and we meet the strict requirements of the Insulating Glass Certification Council (IGCC). Your choices are limitless with Northwestern Glass Fab. Below are some options used in insulated glass:

  • Annealed Glass
  • Tempered Glass
  • Low-E Glass
  • Custom Shapes
  • Muntin Bars
  • Coated Glass
  • Laminated Glass
  • Triple Panes


Annealed glass is the basic product produced by glass manufacturers. It is simply “standard” glass that has not been heat treated or laminated.

Tempered Glass

Tempered glass is glass that has been treated by heat and/or chemicals to increase its strength. Tempered glass provides a stronger and safer option when building codes call for safety glass. Once tempered, this glass is approximately 4x stronger than annealed glass. We temper glass in our facility and meet the SGCC guidelines for tempering glass.

So how do you know it’s really tempered? On each piece of tempered glass, we etch a small logo in one of its corners, showing it has been tempered to meet government standards.

Low-E Windows

Low-emittance glass, otherwise known as Low-E glass, has a thin coating applied to one side to better prevent UV and infrared light from passing through its surface. These virtually invisible oxide layers suppress radiative heat flow, not only lowering the amount of UV and infrared light penetrating into your business or home, but also lowering the amount of heat being transferred. There are various types of Low-E products we offer; each is designed to allow for specific solar gains.

Custom Shapes

With ever-changing interior design styles, opportunities for unique glass designs continue to evolve. Northwestern Glass Fab specializes in custom-cut glass for various projects such as tabletops, showers, display cabinets, shelving, mirrors, entryways, and more. Our professionals can work with interior designers, manufacturers, and builders to create custom works, no matter the measurements or pattern.

Muntin Bars

Glass window muntin bars not only add elegance to your window design, but they also add stability to the glass window. Most homes – and sometimes businesses – utilize the traditional grid pattern for their windows, but there are various patterns available to give your design an extra pop. Enhance the building’s exterior appearance by incorporating one or more of our available grid patterns into the windows.

Ready to get started? Install the absolute best insulated glass units for any property with our industry-leading insulated glass units. Northwestern Glass Fab has been providing our clients with fully-customized insulated glass options for over 100 years. Contact us today at 763-762-1750 to get started.