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.