An insulating glass spacer is placed within the unit to separate the two or more plies of glass. Viracon’s insulating glass spacers are available in two colors, three materials and a variety of thicknesses. When specifying an insulating glass unit, it is necessary to specify all three; color, material and thickness.


Color choices include; black or silver mill finish depending on the spacer type. Black spacers are being specified more often today, as designers prefer the clean look this option provides. The color black tends to blend with the gaskets and framing which minimizes the overall visual impact by leading occupants to look through the glass rather than at the framing or spacer. The color of the spacer does not affect the solar performance of the insulating glass.


The thickness of the spacer will determine the distance, or space, between the two glass plies in an insulating unit. Viracon’s typical 1” insulating units are constructed using a 1/2” (13.2mm) nominal thickness spacer; however a wide variety of alternate thickness spacers is available. Even a minimal change in the thickness of the spacer can affect solar performance so it is important to include the thickness in a specification.

Spacer Illustrations


spacer u-factor by Viracon


When selecting a spacer material it is necessary to be aware of the different u-values used in the glass industry. Center-of-glass (COG) u-values represent the center of the glass. Center of glass values provide an effective way to directly compare glass products without bias from spacer material, framing or unit size. Edge-of-glass (EOG) values represent the perimeter of the glass unit affected by the spacer material. Framing the glass unit is installed into also has a separate value. These values are weighted based on the area of the unit to provide an overall u-factor. The overall value is typically an input needed to run whole building energy calculations and determine code compliance.

Aluminum, Stainless Steel and Viracon Thermal Spacer (VTS™) are the three spacer material options available from Viracon.

Although aluminum was once the most specified, increasing energy requirements are escalating the demand for alternate spacer options to improve edge of glass (EOG) u-value. Spacer materials that improve the EOG u-value beyond the performance offered by aluminum are commonly grouped together under the category of warm edge spacers or warm edge technology.

Spacer Performance-2 by Viracon - delivers a customized architectural glass solutions

Aluminum has been available for decades and provides a basic level of performance.

Stainless Steel is one warm edge spacer option offered by Viracon. Stainless steel is less conductive than aluminum and has one-tenth the thermal conductivity of aluminum.

Viracon Thermal Spacer (VTS™) is Viracon’s newest and most superior warm edge spacer. VTS™ is a proprietary formulation consisting of black thermoplastic with integrated desiccant and primary seal that is chemically bonded directly to the glass and secondary sealant. VTS replaces the traditional spacer, desiccant and primary sealant with a single, better-performing component available in sizes up to 130” x 236”. Argon fill is included and a secondary sealant is applied. VTS carries a special 12 year insulating warranty.   Viracon Thermal Spacer  


Please use this chart as a guideline when selecting spacer color, material and thickness. Note:
  1. Aluminum, Stainless Steel and VTS™ can be used in spandrel applications.
  2. Viracon offers pressure adjusted insulting units suitable for elevation changes between manufacturing location and installation site, if required.
  3. Black painted and black anodized finishes are interchangeable.


Spacer materials that improve the u-value beyond the performance offered by aluminum are commonly grouped together under the category of warm edge spacers or warm edge technology. Below is an example of the improvement in thermal performance that can be obtained by using Viracon's warm edge spacers; Viracon Thermal Spacer (VTS™) and Stainless Steel. Spacer Performance Note:
  1. Center of glass u-value is calculated using WINDOW 7.0 software.
  2. Rough opening u-value is generated by using thermal model simulation software, incorporating a thermally enhanced framing system.
  3. Condensation Resistance (CR): A relative indicator of a fenestration product’s ability to resist the formation of condensation at a specific set of environmental conditions. The higher the Condensation Resistance value the greater the resistance to the formation of condensation.

Viracon cannot guarantee the future availability of component parts manufactured or supplied by others that are incorporated into Viracon products.