Optical property testing for IGDB / CGDB submission
OTM is eligible to perform material optical property testing for International Glazing Database (IGDB) or Complex Glazing Database (CGDB) submission. This article aims to explain the testing procedures for IGDB or CGDB submission purposes.
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IGDB optical property testing
What is IGDB?
IGDB, or International Glazing Database, is an optical property database of specular glazing materials. The IGDB is maintained by LBNL and more information about the IGDB is available on this website.
The IGDB is primarily used in the NFRC fenestration performance rating program. It is required to submit the optical data of glasses to the IGDB before they can be used as the inputs in the NFRC certification simulations.
IGDB testing procedures
The IGDB testing procedures are based on NFRC 300 and 301. They are identical to the procedures for single glazing optical & thermal properties testing. The details are not repeated here and please expand the block below for the key steps.
The IGDB is for specular glazing materials only. Below are a few typical examples:
- Monolithic glasses (uncoated glasses)
- Glasses with coating
- Glasses with window film
- Laminated glasses
For insulating glazing units (IGUs), individual glass panes need to be tested one by one.
On completion of the test, a text file in the IGDB format is provided for submission. Shown below is an example.

Please expand the block below for more information.
CGDB optical property testing
What is CGDB?
CGDB, or Complex Glazing Database, is an optical property database of non-specular window shading materials (such as shade fabrics). The CGDB is also maintained by LBNL and more information about the CGDB is available on this website.
The CGDB is primarily used in the AERC window attachment rating program. It is required to submit the optical data of window shading materials to the CGDB before they can be used in the AERC certification simulations.
CGDB testing procedures
The CGDB testing procedures are based on AERC 1.1. There are two steps in the CGDB testing:
The CGDB is for non-specular window shading materials, typically shade fabrics. A shade fabric material sample is shown in the photo below. The testing procedures described in this article are based on shade fabric materials and they may not be fully applicable to other window shading materials (e.g., insect screens, cellular shades, or Venetian blinds). OTM cannot test glass frits at this moment, due to some instrument limitations.

Homogeneity testing
Unlike specular glazing materials in the IGDB, non-specular window shading materials may be with greater sample-to-sample variation. It may not be appropriate to randomly pick up a sample to present a product. The homogeneity testing is therefore required to quantity the sample-to-sample variation of a product statistically and select a representative sample.
There are 3 steps in the homogeneity testing:
- Sampling
- Visible light transmittance or reflectance measurement
- Homogeneity calculation
1. Sampling: 18 samples need to be sampled from different production lots and different positions (as specified in AERC 1.1).
2. Visible light transmittance or reflectance measurement: The visible light transmittances or reflectances of the 18 samples are measured.
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3. Homogeneity calculation: the material product homogeneity is then calculated statistically from the measured visible light transmittance/reflectance results. Based on the homogeneity calculation results, a representative sample is then selected from the 18 samples in Step 1 for the optical property testing.
Please expand the block below for more information.
Shown below is a sample homogeneity test calculation report (in this example, sample #3 is selected as the representative sample).

There are also additional procedures defined in AERC 1.1 for the following scenarios: 1) newly developed materials; 2) materials in a material product family; 3) materials under the recertification process. Please expand the block below for more information.
Optical property testing
As the CGDB is for non-specular window shading materials, there is a diffuse component of the spectral transmittance/reflectance.
The are 3 steps in the optical property testing:
- Direct-hemispherical and diffuse spectral transmittance/reflectance measurement
- Thermal emissivity and infrared (IR) transmittance measurement
- CGDB format file generation
1. Direct-hemispherical and diffuse spectral transmittance/reflectance measurement: there are in total 4 measurements for each sample. The instrument used at OTM is a UV/VIS/NIR spectrophotometer with 150 mm integrating sphere. The wavelength range is 300 nm – 2500 nm.
Please expand the block below for more details.
2. Thermal emissivity and infrared (IR) transmittance measurement: the thermal emissivity and IR transmittance of the both sides of a sample are measured with a portable emissometer.
Please expand the block below for more details.
3. CGDB format file generation: the measurement results in the previous two steps are written to a text file in the CGDB interim file format for submission.
Shown below is a sample text file in the CGDB interim file format.

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Last update: 24/04/2022
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