CGDB Diffuse glazing submission process
Diffuse glazing covered by this process is defined in the scope of NFRC 300 as "Homogeneous diffusing materials are covered using this test method with special consideration for diffusing samples when noted. Examples of products in this category are fritted glass, diffusing interlayers, and diffusing applied films. The product should be homogeneous on a large scale, i.e. it should not matter significantly where on the sample a measurement is carried out. It does not matter if the scattering is generated in the bulk of the material or by surface roughness." Interlayers are submitted as laminates rather than the interlayer by itself, just like for IGDB.
The process can be broken down in five smaller steps:
- Measure data according to the diffuse glazing procedures in NFRC 300/301.
- Format the data in text file(s) according to the interim CGDB data format.
- Test that the text files can be imported into WINDOW 7.8.55 or later.
- Fill out CGDB data submission spreadsheet.
- Email submission spreadsheet and files to CGDB@lbl.gov.
Step 1. Measure data
The test lab carrying out the measurements must have completed the most recent diffuse glazing ILC.
The full procedure is detailed in NFRC 300 and NFRC 301 but some key difference between specular measurements are:
- A large aperture integrating sphere (100mm) must be used to measure the normal-hemispherical properties.
- Spectral data for 8 spectral properties should be reported, all combinations of transmittance/reflectance, front/back, and normal-direct/normal-diffuse.
- Emissivity of rough surfaces can be measured using an emissometer as specified in NFRC 301 and reported as a single integrated value.
Step 2. Format the data in text files
The interim text file format is an extension of the IGDB submission file format. There are also examples in the file area at the bottom of the page. To make the files more human readable the examples have a header line with column headings for the data. WINDOW does not parse this definition, i.e. you cannot modify that line and provide different data columns. Note that samples with coated rough surfaces can use the emissivity header value instead of following the IGDB requirement of having spectral IR data for coated surfaces.
For now you are not allowed to specify the IGDB ID number/CGDB number. The CGDB is separate from the ID blocks that manufacturers received for IGDB.
Step 2b. Workaround for partially covered products
WINDOW does not yet have a built-in way to mix a 100% and 0% covered (substrate only) products. Rather than forcing measurement of patterned products we allow submitters to manually make and submit partially covered products by averaging 100% and 0% covered measurements the appropriate amount and submitting the result as a separate record. A zip-file with examples and a spreadsheet demonstrating the calculation is available for download.
Step 3. Verify the text file
Import the text file in WINDOW. This is done in the Shade Material Library. When you click import, you select Dir/Dif text file format from the drop and then browse to select your file(s).
Once it is imported you can review the integrated values in the Shade Material Library. This step is important as WINDOW might not catch all formatting errors in the file.
Upon import a corresponding layer is created in the Shade Layer Library. You can then create a glazing system with the Shade Layer that was created. In the Glazing System Library you select the layer type Shade or frit and then add the layer you imported.
WINDOW allows for faster calculations in the Optical Calculation preferences. For testing it is recommended to use condensed spectral data with 5 visible and 10 IR bands with the W6 standard basis. Use full spectral data for more accurate calculations.
Step 4. Fill out the CGDB submission spreadsheet
Download the latest version of the CGDB submission spreadsheet (v1.38 or later) and fill out the relevant tabs (General Information, New-replacement-delete, and Diffuse glazing) . A field for CGDB number was included in case we change our mind about allowing submitters to assign ID numbers please ignore for now.
Step 5. Email submission spreadsheet and files to CGDB@lbl.gov.
Similar to how IGDB submissions are sent in this goes via email. Please do not mix CGDB and IGDB submissions.
CGDB Venetian blind submission process
CGDB stores information about Venetian blind products in two libraries. The properties of the slats, such as reflectance, are stored in the Shade Material Library, and the combination of the slat material and geometry of a blind is stored in the Shading Layer Library. The geometry shown in the image below includes information about slat width, rise(which defines the curvature), spacing between the slats, and the tilt angle (positive when the right side of the slat is higher than the left side, where the right side is the room side of the window). The thickness t is stored in the Shade Material Library with the spectral data, emissivity and conductivity of the slats.
There are two main steps, 1) adding the slat material to the Shade Material Library, and 2) defining the blind geometry and referencing the appropriate Shade Material and storing that information in the Shading Layer Library.
Measuring and submitting slat spectral data for the Shade Material Library
This step is only required for slat materials not already in the CGDB Shade Material Library.
Requirements for the slat to work with the Venetian blind model in WINDOW are:
- The slat material is opaque. The perforation used to suspend the blinds can be ignored.
- Both front and back surface are diffuse, e.g. painted. Unfinished aluminum is typically too "mirror-like" to work with the model.
- The geometry has no more than a single curve (flat is fine, but no "S" or "W" like shapes).
- The slats are thin compared to the gap between the slats.
A more detailed document showing the measurement process and how to format the data available on the data submissions page linked below.
|Test Lab Name||Contact e-mail|
|Optical Data Associates, LLC (Tuscon, Arizona)||email@example.com|
|Mermet Fenestration Lab (Cowpens, South Carolina)||Nathan.firstname.lastname@example.org|
|Fraunhofer ISE TestLab Solar Façades (Fraunhofer, Germany)||email@example.com|
|Sonnergy France (Paris, France)||firstname.lastname@example.org|
|China Building Materials Test and Certification Group Co., Ltd. (Beijing, China)||email@example.com|
|OTM Solutions PTE Ltd (Singapore)||Chen.firstname.lastname@example.org|
Simulating and submitting a Venetian blind definition for the Shading Layer Library
Multiple Shade Layer records for Venetian lbinds can be defined for different geometries using the same record from the Shade Material Library as needed. To obtain NFRC approval for the Shade Layers, the Shade Material needs to have NFRC approval, i.e. the "#" needs to be associated with the Shade Material record.
A WINDOW database (Microsoft Access MDB file) containing the desired Shade Materials and Shading Layers should be submitted to LBNL for inclusion in the CGDB.
A detailed document has been prepared in collaboration with NFRC for the required layers to be created. That document holds information about which angles to test at and naming conventions to maximize the information contained in the Shade Layer name. If a fully closed angle greater than the default (70 degrees) is used the submission must include documentation demonstrating how the hardware accomplishes this.
When submitting the data to the CGDB, the WINDOW database (.MDB file) should be accompanied with a datasubmission spreadsheet. Use the most current version of the spreadsheet. The key components to fill out is the geometry definitions for the Shading Layer and the Shade Material used for each Shade Layer.
Regarding the WINDOW database submitted, please refrain from including more records than are needed. See the Knowledge Base article about creating a Project Database which will allow only the needed records to be included in the database.
The process of submitting spectral data and layer information within one CGDB cycle
A simulator cannot build an approved layer using slat data that is not in the CGDB Shade Material Library. To avoid taking two CGDB release cycles to get a new slat material and blind layer into one CGDB submittal requires that the submitter put in some extra effort. The manufacturer is responsible for coordinating the submittal first of the slat material in the Shade Material Library for technical review by LBNL and then second, defining the Shading Layers using the Shade Material. The manufacturer needs to communicate the intent of the 2-part submission with LBNL in order to keep the process on schedule for the final CGDB release.
The steps for completing this submittal in one cycle are the following:
Submit the slat material data to LBNL 1 month prior to the official CGDB submission deadline (see schedule at the bottom of this accordion).
LBNL will produce a peer review WINDOW database with the slat material in it that a simulator can use to create the records in the Shading Layer Library.
The WINDOW database created by the simulator (which includes both the needed Shade Material library and Shading Layer library records) is then submitted to LBNL by the official submission deadline which means that both the slat material and the Venetian blind Shading Layer can go to peer review in the same cycle.
Do not hesitate to contact CGDB@lbl.gov with questions.
Standards such as ASTM903, NFRC 300 (updated in 2020 to include diffuse glazing), ISO9050, and CEN 410 include information about how to measure spectral data and they are useful for specular glazings, but not so much for light-scattering products.
Data for the CGDB is measured and provided based on the product type.
In the files section of this page (see below) you can download detailed documents showing how to measure a specific product.
Opaque Diffuse Venetian Blind Slats
With version 6 of WINDOW it was possible to include a layer of Venetian blind slats based on the reflectance of the slat. However, the radiosity model used does not work for specular or transparent slats. The document describes limits for how to determine opaqueness and sufficient diffuseness of the sample.
AERC 1.1 is a technical document specifying how to measure shade fabrics that are published in the CGDB Shade Layer and Shade Material libraries. Documentation of the Solar BSDF creation process from measured data is available below in the file section.
Homogeneous isotropically scattering diffuse glazing is covered by NFRC 300 and 301 after 2021, more details on Diffuse Glazing dropdown of this page.
|Measurement of Blind Slats for CGDB||222.37 KB|
|Solar BSDF documentation.pdf|
What is a Bidirectional Scattering Distribution Function (BSDF)? Why should you care? For present purposes we can use a one-sentence nontechnical explanation: The BSDF is just a complete collection of transmission and reflection factors, one for each combination of incoming and outgoing directions. The really important question is how the BSDF is used and how a manufacturer will ever be able to get all that data together for each product. The situation is not nearly as bad as it looks.
For visualization of BSDFs there is a web based interface at https://www.ladybug.tools/bsdf-viewer/
WINDOW6 calculates a BSDF matrix for a glazing/shading system from the BSDF matrix of the individual component layers. The W6 program was created on this platform because it is the most general approach to the problem of combining multi-layers. In cases of low symmetry this generality may be necessary to carry out an accurate combination of layers. In many other cases however it will be possible to measure the properties of the materials in much less detail.
- Example 1, specular materials: WINDOW5, which operates on specular glazing layers only, has a simplified ray tracing algorithm which can only operate on a small subset of optical factors. In essence, the assumption is made that scattering is nonexistent and does not even have a place in the algorithm. In WINDOW6, where scattering is assumed to be present in general, specular glazing becomes a special case so that the specular glazing factors are just the diagonal elements of the BSDF matrices. Thus the BSDF matrix does not have to be completely filled by the user. When specifying a specular material, WINDOW6 simply fills the non diagonal elements with zeros. That is the specular sub model for WINDOW6.
- Example 2, diffuse materials: For a material which is close to perfectly diffuse (Lambertian) or which has a specular component combined with a Lambertian back grounded, it is often acceptable to assume that the measured total diffuse component is evenly distributed in space and in the BSDF matrix. So in many cases a greatly reduced set of initial measurements may be adequate although WINDOW6 by its nature will first fully populate the BSDF matrices before performing any multilayer calculation, and then perhaps throw most of it away when reporting the final results. Thus contributors to the WINDOW6 database need not fear that they will be forced to measure 10,000 optical quantities where 10 such measurements were sufficient for the specular case of WINDOW5.
- Example 3: If you have something crazy like a hologram or a diffusing material that seems not to be uniformly diffuse, then you can measure as much data as you think you might need and populate the BSDF matrix accordingly. The point is that WINDOW6 can handle arbitrary complexity but it can often make do with a lot less.
For these reasons I urge the data supplier not to think too much about BSDFs. Consider it an internal data array in WINDOW5/WINDOW6 or similar programs with the details best left to programmers. Come up with as much directional data as practical. It might be enough for accuracy of combination.
The following are specific requirements for different product types.
During 2018 we will be using a text format for submitting data of diffuse samples that are characterized with direct-direct and direct-diffuse spectral properties. The format is an extension based on the current IGDB format. The main difference between the two formats is the number of data columns. Examples of how files look for different products are available in the file section at the bottom of this page.
Venetian Blind Slats
Venetian blinds (horizontal louvered shades) can be simulated in WINDOW using the ISO 15099 model combined with the multi-layer matrix method (Klems 1994). These methods require optical properties of slat material as follows:
- Both front and back surfaces are diffuse (e.g. painted). Unfinished aluminum is typically too specular (mirror-like) to work with the model.
- The geometry has no more than a single curve (flat is fine, but no "S" or "W" like shapes).
- The slats are thin compared to the gap between the slats. Typical geometries are less than 1 mm thickness to a 15 mm gap between slats and that is fine.
- The perforation used to suspend the blinds can be ignored.
Note: Experiment with the WINDOW 7 shade layer interface for Venetian blinds to see what geometries are possible and what information is required. If your product meets those requirements it can be included in the CGDB as a shade material and shade layer.
See the subpage in the menu to the left to find complete documentation of measurement, submission, and simulation.
Shade Screens and Cellular Shades (Fabric Type Materials)
- The fabric is thin (i.e., less than 1 mm).
- The pattern scale should be no more than 2 mm or much larger than 25 mm.
- The material is effectively flat.
- If the product consists of more than 1 fabric, each fabric needs to be measured individually (e.g., for a cellular shade, front, back, and glue line could each be a separate fabric)
- If the fabric has different front and back properties, the front should be clearly marked. The front surface corresponds to the exterior surface, i.e. the surface seen from the outside of the window.
- The screen material is thin.
- The screen has a regular pattern of circles or rectangles.
- The unperforated material is homogeneous.
- The material is effectively flat.
Fritted Glass, Diffuse Laminate Interlayers, and Patterned Glass
These classes of products do not have a good pathway for measurement right now. The standard 150 mm integrating spheres have proven to be insufficient in several different inter-laboratory comparisons and it is well understood why. An NFRC task group is investigating the use of 270 mm spheres (and larger) as well as goniophotometers as alternatives.
Submitted data are subject to peer review. Members of the peer review group will get an email notification that the peer review files are ready for review. The schedule below gives the start and end time for the peer review, defining a time window to provide comments for each release cycle.
To join the peer review group please send an email to CGDB@lbl.gov.
There is a wide range of different products in the CGDB which leads to multiple different steps to review the data. All data is shared in a WINDOW database so that the peer reviewer can interact with the the data using WINDOW. Furthermore the peer review comes with PDF documents with tabulated data showing integrated values for added Shade Materials, as well as graphs of the spectral data. However, Shade Layers that are built from materials, e.g. Venetian Blinds layers, are not present in the spectral data graphs and tables, only the slat material properties show up there. WINDOW has to be used to review the geometry of such layers.
There are currently four CGDB releases per year. Data submitters should follow the schedule below for their data submission. Due to the short processing time, we will no longer accept more than 40 submissions or requests for modification/change from each manufacturer, in each cycle.
|Release Number||Submission Deadline||Data Goes to Peer Review||End of Peer Review||Release Date|
LBNL is working on measurement procedures for different scattering products. After the publication of measurement procedure(s), an inter-laboratory comparison (ILC) will be conducted. The ILC is expected to be completed, and a full report published, within a year of its commencement. Upon completion of a successful ILC, with at least 1 commercial laboratory showing competence, commercial measurement of scattering systems will be approved.
Currently, LBNL is measuring optical properties of scattering products for a number of different materials and product types. Please send your request with completed submission form. Please contact CGDB@lbl.gov for a quote, lead time, and shipping address of your samples.