Insulated Glass Informational

Insulated Glass (IG) units are hermetically sealed combinations of two or more lites of glass separated by a dry airspace. IG units improve thermal performance, significantly reducing heating and air conditioning costs. IG units also reduce interior condensation in cold climates.

Where to use it?

  • ¬†Fixed and Operable windows
  • Storefronts and Curtain Walls
  • Sloped/Overhead Glazing
  • Non-vision (Spandrel) Locations


Insulated glass units are fabricated according to project specifications. IG units can be constructed using a large variety of glass products to achieve desired aesthetics, meet design criteria, safety codes and/or to improve solar control and thermal performance. Glass options include clear, low iron, Low-E’s, standard or high performance (spectrally selective) tints, reflective, silk-screened, spandrel, laminated, decorative and wired glass. The glass lites of an IG unit can be annealed, heat-strengthened, tempered or laminated.

The standard 1″ commercial IG unit consists of two lites of 1/4″ glass and a nominal 1/2″ air space. Custom IG unit designs can be fabricated with glass thicknesses ranging from 1/8″ to 3/4″ and with airspace thicknesses ranging from 3/16″ to 7/8″ having standard spacer colors of clear, bronze and black anodized, and mill finish aluminum. Maximum sizes for IG units are determined by a number of considerations including thickness, weight, aspect ratio, application and load requirements.

Insulated glass units are used in essentially all exterior building applications, including vertical glazing, sloped glazing, overhead glazing and skylights, and also in both vision and spandrel (nonvision) areas. Depending on the glass type used, IG units can be designed for: light and solar control, sound control, ultraviolet screening (to reduce fading), hurricane, earthquake and blast resistance, security, bullet resistance, and decorative applications.

They can ALL be etched!
Hurricane resistant = Usually laminated & tempered combined (depending on location). A whole lot of hurricane resistance is being sure the glass stays in place in extreme conditions, wind loads, etc, and has added impact resistance. Very often, it passes specs if it is simply Laminated glass with deeper capture. (Trim molding)

Low E = A glass that is coated with a very thin metallic film, (usually not visible to the naked eye), that reduces solar gain by reflecting energy back outside, instead of letting it inside the structure. These coatings are quite fragile and are usually used inside insulated glass units (IG’s). Therefore, if you are sandblasting on the outside of an IG unit, you will not affect the coating.

Always suggest to the customer-
1- Etch the glass first, then assemble the IG unit. A unit has at least 4 (double pane), and as many as 6 (triple pane) surfaces. Standing on the outside of the structure, the surface you can touch is the first surface. The other side of that piece of glass is the second surface. Then there is an air space, (sometimes inert gas), and another layer of glass, surfaces 3 & 4. In the case of triple pane, there is another air layer, then surfaces # 5 & 6, 6 being the glass you can touch from inside the structure. (Sidenote– Laminated glass is made from multiple layers of glass laminated together constituting ONE piece of glass, and can easily be incorporated into any IG unit.)

2- Low E is typically used on the # 2 surface, to reflect radiant heat before it saturates the unit. For an etched unit, I always suggest the etching go on the # 2 surface, moving the low E to # 3. This allows the heat gain from the etching to be dissipated into the dead air space, and the low E to still do it’s job, while encapsulated in the unit. Etching will catch much more heat gain than clear glass, and you want that gain dissipated BEFORE it gets to the inner surface. In the case of triple pane, 5 & 6 should just be glass, though differing thicknesses will ameliorate sound transmission.

3- For Hurricane/blast resistance, ALL of these variables must be completed BEFORE installation, to ensure compliance. My only exception would be when a customer brought the entire assembly to me, wanting the etching on an outer surface.

“Tinted” Glass

The glass will be clear, colored, or tinted. Commonly, the available colored glasses are Bronze,(brownish), Grey, (blackish), and nowadays, there are a few green variations. Tinted usually refers to a glass that has had a film applied to it’s surface (like the inside of car windows). If you are presented with “tinted” glass, be sure to do your work on the UNTINTED side, or you may find yourself having the glass re-tinted!

Copyright 2013 – Arizona Glass Classes

June 2021
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