CGDB Interlaboratory Comparison


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CGDB Interlaboratory Comparison 

To be allowed to submit data the measurement equipment used must pass an inter-laboratory comparison (ILC) at least every four years. This means that if you measure your own data you have to participate. If you are using a test lab, the test lab has to participate.

Due to the large number of CGDB submitters these ILCs are typically parallel, i.e. each participant will get their own set of samples. 

The following properties of the data are required to pass the ILC:

  • Data should be physical, i.e. transmittance should be in the interval from zero to one.  An exception is noise that for extremely low or high values records as outside the physical values, these values are acceptable as long as the smoothed values are physical.  
  • There should be no systematic errors in the data, such as, but not limited to, discontinuities and absorption artifacts.
  • As a rule of thumb data should be within two standard deviations of the average to not be considered an outlier. This might vary depending on what property is being studied, the magnitude of the value, and the magnitude of the variance in the sample.

Laboratories that submit data to the Complex Glazing Database (CGDB) have to participate in an inter-laboratory comparison (ILC). This a procedure that allow both contributors and database maintainers to confirm that the measurement capabilities of the laboratories are of high quality.

This is the first time the procedures in AERC 1.1 is used in an ILC, so the result is expected to be used as a measure of the accuracy of the methods of AERC 1.1.


The goal of the ILC is to make sure the submitting laboratories populate the CGDB with accurate data as well as learn about the accuracy of the methods written in AERC 1.1. In past ILCs, LBNL has been working with outliers trying to make sure they measure accurately and that is still our mission.

Questions and answers

11/3/2017 - Are the instructions written yet? Yes.

11/13/2017- The instructions specify that the labels are on the back of the samples, but the label reads front, please clarify. The label is correct, the instructions are updated in v1.1.

11/13/2017- Can you specify the blind manufacturer for sample 5? Unfortunately no, I saved those from being thrown away, and there were no identifying marks left.

11/13/2017- AERC 1.1 specifies a requirement of the sphere aperture that implies that only circular ports are allowed, is that intended? No, rectangular ports of similar size were not intended to be disqualified. The open part of the question is what the minimum side of the port has to be, this is crucial as it influences the maximum possible beam size. And as the beam size in turn influences how well inhomogeneous samples are characterized there should be a minimum specified. Hopefully some rectangular ports measurements will be submitted and provide information about this.

6/1/2018 - Are the values in the emissometer workbook seems very wrong? Mostly yes, they were filled out to verify that the connections to equations were working.

6/13/2018 - Second emissivity datasheet uploaded, this is required to complete for passing the emissivity portion of the ILC.

Related Downloads: 

Attachment Size
PDF icon AERC ILC 2017 Instructions1.1.pdf - Firstrevision of the instructions 125.47 KB
Office spreadsheet icon Workbook_AERCILC2017_boxNN.xls - Clean workbook v1.1 184.5 KB
File AERCILC2017EmissivityWorkbook_boxNN.xlsx - Emissivity work book for emissometers 157.17 KB
File Test lab registration form 33.28 KB
2019 Complex glazing ILC

A complex glazing ILC was conducted as part of an NFRC funded research project during 2019-2021. All instructions and the final report can be found in the file section below.

The outcome laid the ground for updates to NFRC 300 and NFRC 301 to include procedures for light-scattering glass products such as fritted glass, acid-etched glass, sand-blasted glass, laminates with diffuse interlayers, and diffuse applied films.

Providing accurate results in this ILC is needed to be approved for submitting glazing data to the CGDB. (Process for this still pending updated WINDOW version supporting the new file format)

Related Downloads: 

Attachment Size
PDF icon CILC2019report.pdf 845.99 KB
PDF icon CGDBInterimFileFormat_Definition_v1.06.pdf 673.98 KB
PDF icon Instruction for ILC participants 597.14 KB
Plain text icon Example submission file 38.07 KB
Plain text icon Example submission file 53.5 KB
File Workbook for submitting instrument information 11.8 KB