Vi at Silverstone

SGH surveyed the windows and observed fogging as the most common discoloration, but also observed copper-colored marks within the insulating glass units (IGUs). We performed field testing on twenty windows to estimate frost points and evaluate the IGU seals. The twenty windows were then transported to our laboratory for further testing, including the following:

• Confirming seals were intact and the insulated cavity was not compromised during transport
• Estimating frost and dewpoints of the sample IGUs
• Applying several testing methods to identify the components of the IGUs
• Using our scanning electron microscope to identify the low-emissivity (low-e) coating composition and identify the inorganic chemical composition of the paints on the interior muntin centered in the IGU
• Using our Fourier Transform infrared spectrometer to identify the composition of the three sealants and examine the fogging
• Performing plasticizer extractions of the primary and interior sealants to determine the plasticizer percentage

To supplement our laboratory testing, we engaged an independent laboratory to perform additional plasticizer extractions, identify organic components in the sealant, and identify volatile organics in the air sampled from a sealed IGU.

SGH concluded fogging resulted from evaporating sealant plasticizers depositing on the glass and was exacerbated by ultraviolet light exposure. We determined the copper-colored discoloration was likely related to the muntins impacting the glass and scratching the low-e coating. Since the fogging would continue as long as the sealant plasticizer remained, we recommended replacing the windows and prepared a specification for the replacement.