Quantifying Argon concentration within insulating glass units using low frequency ultrasonic technique

• Novel non-destructive ultrasonic method to quantify Argon concentration in IGUs. • UT methodology shows high accuracy, achieving MAE of 0.13 and R 2 of 0.99. • The proposed methodology outperforms SES and HIGC devices in measuring Argon in IGUs. • UT energy correlates effectively with Argon concentration across 20 mixtures. • The methodology enables efficient on-site IGU inspections and quality control. Insulating glass units (IGUs) account for over 30% of thermal transmission losses in building envelopes. To mitigate this, IGUs are often filled with low-conductivity gases like Argon. However, Argon concentration decreases over time due to IGU aging and manufacturing processes, which lessens their insulating effectiveness. This study presents a novel nondestructive methodology to quantify Argon concentration in IGUs using ultrasonic technique. The ultrasonic energy transmitted through the IGU is correlated with Argon concentration, validated through both experimental measurements and numerical models using COMSOL Multiphysics®. The models simulate acoustic-structure interaction by adjusting gas density to reflect Argon presence, showing increased ultrasonic energy with higher Argon concentrations. Experimental measurements on two IGU samples with twenty Argon-air mixtures (ranging from 100% to 25% Argon) show that the proposed ultrasonic technique achieves a mean absolute error of 0.13, outperforming Spark Emission Spectroscopy and Helantec ISO-GAS-Control, which have errors of 2.31 and 0.33, respectively.