IGDB Interlaboratory Comparison
IGDB
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IGDB Inter-laboratory Comparison (ILC)
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 IGDB 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.
Part of the ILC is focused on the measurement of IR reflectance used for calculation of emissivity. It is relevant for international participants to be aware that while the NFRC 301 and EN 12898 calculation procedures are different the underlying measurement is the same. So if internal emissivity calculations do not agree with reported values it could simply be due to the difference in calculation method. The difference in calculation method was investigated in an NFRC task group in 2021/22 and a recording of the TG findings was made and is available for download in the file section below.
Related Downloads:
| Attachment | Size |
|---|---|
 Recording of the findings in the NFRC emissivity calculation task group pertaining to the difference between NFRC301 and EN12898 |
LBNL requires data submitters to participate in an inter-laboratory comparison (ILC, also know as round-robin and inter-laboratory study (ILS)) as a way to verify that they understand the procedures and their equipment works.There are multiple ASTM standards describing how to run such an activity, but they are designed to validate the method rather than the labs, so while the procedure described here is inspired by them it is not perfectly described by them.
All submitters shall have successfully participated in the most recent inter-laboratory comparison.
The ILC might be defined to test several different procedures (e.g. solar optical and thermal IR measurements) and should be set up so that it is possible to qualify to perform a subset of all measurements that are tested during the activity.
The outline of the process is as follows:
- Samples selection committee: Form a committee that decides what samples are required to verify the procedures under scrutiny.
- Identify participants: Compile a list of participants to get a lower limit of the number of participants.
- Acquire samples: Acquire samples that meet the specification of the sample selection committee. Each participant needs their own set in a parallel ILC, extra sets are needed to accommodate labs that want to qualify before the next ILC.
- Organizer writes instructions: Prepare instructions on what to measure, and how to report the results.
- Organizer characterizes samples for consistency: Perform limited characterization of all samples to quantify consistency.
- Participants measure: Samples are received, characterized, and then the data is formatted and sent back to the organizer.
- Organizer writes initial report: When a critical mass of participants has responded, an initial report is prepared by the organizer to determine what constitutes accurate results.
- Measurement iteration: Participants that did not qualify get advice on how to improve their measurements.
- Final report: Final report, including lessons learned and suggested improvements on the procedures, is published.
- New participants: Allow new lab to qualify so that they do not have to wait until the next ILC. The organizer sends samples, analyzes results, and makes sure the new participant qualifies. Before the organizer is running out of sample sets, it is advised to require the new submitters to send the box back after they have qualified, effectively turning the final boxes into a serial ILC.
The main benefit of running a parallel ILC is that it takes less time for a large number of participants, but it also allow the participants to have samples at hand to verify maintained accuracy if they update equipment or modify their measurement procedures. The drawback is the sample variation, but handling of optical materials might induce changes to the surfaces, which would make it difficult to analyze the final result.
Inter-laboratory Comparison 2015
Background
All laboratories that measure data that is submitted to the IGDB (International Glazing Database) must participate in an ILC (Inter-laboratory comparison) every four years. This includes laboratories that were approved after the last ILC (four years ago), i.e. laboratories that were included in between ILCs.
In addition to the IGDB submitters there are other institutes that voluntarily participate.
Goals for ILC 2015
The three samples of this ILC aim to cover:
- high and low transmittance
- variation between visible and NIR
- low emissivity
- thick samples
Instructions
Instructions as well as example files will be found in the Related Downloads section below.
- box0_3.txt is an example of how a measurement file might look.
- box0info.txt is an example of how a instrument description file might look.
- boxXinfo.txt is an empty copy of the instrument description file.
NFRC Report
The report presented at the NFRC fall meeting in Denver 2016 is found below.
Inter-laboratory Comparison 2011
Background
All laboratories that measure data that is submitted to the IGDB (International Glazing Database) must participate in an ILC (Inter-laboratory comparison) every four years. This includes laboratories that were approved after the last ILC (four years ago), i.e. laboratories that were included in between ILCs.
In addition to the IGDB submitters there are other institutes that voluntarily participate.
Goals for ILC 2011
In addition to assuring that all participating laboratories are getting accurate results it also covers two specific problems.
The first is deconstruction of laminates and applied films, care was taken to select samples so that the laminates and the unlaminated samples were from the same production run.
The second problem being studied is measurement of thick samples, the thickest laminates are two 6mm pieces plus the laminating layer.
Instructions
Instructions as well as example files are found below.
The only change in v1.0 instructions compared to the initial contains recommendations on cleaning.
- box0_2.txt is an example of how a measurement file might look.
- box0info.txt is an example of how a instrument description file might look.
- boxXinfo.txt is an empty copy of the instrument description file.
Preparation for Complex Glazing ILC
Participants of ILC 2011 will also receive 5 samples with light-scattering/light-redirecting properties. These are not part of ILC 2011 but distributed for a future ILC.
Complex Glazing ILC 2011
Instructions
Instructions as well as example files are found below.
- box0_6.txt is an example of how a measurement file might look.
- box0_reference.txt is an example of how a file describing the reflectance of a calibrated reference sample.
Related Downloads:
| Attachment | Size |
|---|---|
| ILC 2015 Instructions |
141.27 KB |
| ILC 2015 Shipping Letter |
22.59 KB |
 ILC 2015 Examples |
9.49 KB |
| ILC 2015 Report |
285.9 KB |
| ILC 2011 Instructions v1.0 |
130.26 KB |
| ILC 2011 Examples |
8.75 KB |
| ILC 2011 Final Report |
319.37 KB |
| ILC 2011 Preliminary Report |
160.28 KB |
| Complex Glazing ILC 2011 Instructions |
126.32 KB |
| Complex Glazing ILC 2011 Examples |
26.63 KB |
| Complex Glazing ILC 2011 Report |
585.24 KB |
Inter-laboratory Comparison 2019
Background
All laboratories that measure data that is submitted to the IGDB (International Glazing Database) must participate in an ILC (Inter-laboratory comparison) every four years. This includes laboratories that were approved after the last ILC (four years ago), i.e. laboratories that were included in between ILCs.
In addition to the IGDB submitters there are other institutes that voluntarily participate.
Goals for ILC 2019
The three samples of this ILC aim to cover:
- high and low transmittance
- variation between visible and NIR
- low emissivity
- 3 mm thick samples
Instructions
Instructions as well as example files will be found in the Related Downloads section below.
- box0_2.txt is an example of how a measurement file might look (the file exemplifies the format, not the data; i.e. the data is for a different coated sample).
- box0info.txt is an example of how a instrument description file might look.
- boxXinfo.txt is an empty copy of the instrument description file.
NFRC Report
The report will be presented at the NFRC 2022 fall meeting and is posted on this web page. This activity got severely delayed by COVID-19, hence the 2019 start/2022 end numbering.
Related Downloads:
| Attachment | Size |
|---|---|
| Report with ILC2019(2022) results |
464.87 KB |
| NFRC ILC 2019 Instructions.pdf |
87.96 KB |
 box0_2.txt |
18.78 KB |
| box0info.txt |
2.09 KB |
| boxXinfo.txt |
1.61 KB |
| ShippingLetter.PDF |
581.15 KB |