Determining the effects of angle on the infra-red reflectance properties of thin films in architectural glass using the Agilent Cary 630 FTIR

Significance of Infrared Reflectance in Architectural Glass

The application of thin-film coatings on building glass to regulate infrared light transmission and reflection plays a critical role in optimizing energy efficiency. The angle of incident sunlight significantly influences heating and cooling performance, making angular characterization essential for designing effective coatings.

Objectives and Study Overview

• Evaluate the mid-infrared reflectance of coated architectural glass compared to uncoated glass at 10° (near-normal) and 45° (angled) incidence.
• Assess how incident angle affects coating performance under real-world conditions.

Methodology and Instrumentation Used

The study utilized an Agilent Cary 630 FTIR fitted with a 10° specular reflectance accessory and a 45° accessory. A gold-coated slide provided a 100 % reflectance background. Samples were measured in percent reflectance versus wavenumber across the mid-IR range (400–4000 cm⁻¹) with 64 scans at 4 cm⁻¹ resolution.

Key Results and Discussion

• Uncoated sheet glass exhibited nearly identical reflectance curves at both angles, confirming baseline stability.
• Coated glass showed decreasing reflectance at higher wavenumbers when measured at 45°, most notably around 1000 cm⁻¹, indicating strong angular dependence.
• Findings emphasize that solar angle impacts heat transfer through coated glass, informing coating design strategies.

Benefits and Practical Applications

• Enables targeted coating development to enhance interior heating in colder climates or reduce heat gain in warmer regions.
• Combining lab-based FTIR measurements with the handheld Agilent 4100 Exoscan allows on-site evaluation of large or installed glass panels for QA/QC and maintenance.

Future Trends and Potential Applications

• Integration of UV-Vis-NIR and mid-IR data for comprehensive spectroscopic characterization of advanced coatings.
• Development of adaptive coatings with tunable angular reflectance properties.
• Expanded use of portable FTIR systems for real-time, in situ monitoring of building envelope performance.

Conclusion

Characterizing the angular dependence of mid-IR reflectance in coated architectural glass provides valuable insight for optimizing energy-efficient glazing solutions. Agilent’s in-lab and mobile FTIR platforms deliver versatile tools for research, product development, and field quality control in the glass industry.