Nondestructive Assessment for Detection of Low-E Coatings on Insulating Glass Units

Insulating glass units (IGUs) are widely used in buildings due to their enhanced insulation properties and energy efficiency capabilities compared to single-pane windows. Low-emissivity (low-E) coatings are designed as an application on IGUs to reduce the penetration of infrared and UV radiation into the buildings without compromising the daylight exposure. However, these coatings can degrade over time due to environmental exposure, reducing their insulating effectiveness, which leads to increased energy loss and diminished occupant comfort. Therefore, detecting the presence of low-E coatings in IGUs becomes important for evaluating and maintaining their efficiency. To this aim, this study conducts a nondestructive evaluation (NDE) approach, utilizing low-frequency ultrasonics. The objective is to detect the low-E coatings on IGU samples. This research evaluates three IGUs equipped with three different low-E coatings, namely double silver low-E, triple silver low-E, and hard coat low-E, and compares their performance with that of a Clear or non-coated IGU as a reference sample. The main parameter evaluated in this study is the Time of Flight (ToF) to compare it across four samples of IGUs. Findings indicate that the presence of coatings results in reduced ultrasound wave velocity or an increase in ToF. Notably, due to the difference in coatings’ thickness, the hard coating presents longer ToF compared to other coatings. This research holds the potential to support retrofit actions aimed at not only reducing energy losses through IGUs but also enhancing thermal comfort for occupants.