Expert in Optical & Thermal Measurement Solutions
We are able to test the daylight reflectance of full-size solar panels. Shown below is an example.
All typical commercial solar panels can be tested, including panels greater than 1.2 m x 2.4 m in size. The results reported are the same as our standard daylight reflectance testing service (sample report). Due to the extra effort in handling such large and heavy samples, some large-size sample surcharge is applicable.
We have a post on how to import user IGDB format file into LBNL optics. The next step is to import the user database created into LBNL WINDOW for further calculations. Please refer to the steps below for the operations.
In the “File” -> “Preference” -> “Optical Data” tab, browse the Optics user database file and set it as the optical data source, as shown below.
In the glass library (“Libraries” -> “Glass”), click “Import” (in the “List” view). In the pop-up window, set the format as “IGDB or Optics User Database”, as shown below. The optical data entries in the Optics user database can then be imported in the next pop-up window.
We are a Singapore-based third-party test laboratory, providing lab test services of material optical & thermal properties. We use Thermtest HFM-100 heat flow meter, with the following key information.
We’ve just released our Q3/2022 OTM Insights newsletter, with the main article “Solar control window film and glass optical & thermal performances“.
Please click the image below to read the newsletter. For the past issues, please proceed to our branding & publications page.
In the daylight reflectance test, the specular daylight reflectance is calculated as:
Specular daylight reflectance = Total daylight reflectance – Diffuse daylight reflectance
Due to the rounding operations, the reported specular specular daylight reflectance could be:
Specular daylight reflectance = Total daylight reflectance – Diffuse daylight reflectance ± 0.001
Shown below is an example result set, with this ± 0.001 discrepancy:
Some customers expect that the specular daylight reflectance should be 0.216 – 0.200 = 0.016 (1.6%) and suspect that there is a typo in the test report.
Our daylight reflectance test reports are generated by in-house software automatically. The ±0.001 discrepancy is not due to a calculation mistake or a typo, but due to the rounding operations, as illustrated in the table below:
| Before rounding | After rounding | |
|---|---|---|
| Total daylight reflectance | 0.2156 | 0.216 (21.6%) |
| Diffuse daylight reflectance | 0.2004 | 0.200 (20.0%) |
| Specular daylight reflectance | 0.0152 | 0.015 (1.5%) |
The luminance contrast test is always in terms of two samples in a pair, typically one bright color sample and one dark color sample. There are two scenarios for sample preparation:
For side-by-side flat surfaces, two flat-panel samples need to be submitted. Shown below is an example:
The preferred sample size is 100 mm x 100 mm or slightly smaller. The maximum sample size is 300 mm x 300 mm. Only 1 pair of samples (2 pieces) are needed and it is optional to provide additional samples as the backup.
For Tactile Ground Surface Indicator (TGSI) studs on a flat surface, it is possible to submit the samples as either integrated samples or loose samples.
Shown below is an example of an integrated sample of TGSI studs on a flat surface:
The preferred sample size of the integrated sample is 100 mm x 100 mm or slightly smaller. The maximum size is 300 mm x 300 mm. Only 1 sample is needed and it is optional to provide additional samples as the backup.
It is possible to submit TGSI studs and flat surface samples separately, without fixing them. Shown below is an example.
It is recommended to provide 2 – 5 loose TSGI stud samples.
For the flat surface sample, the preferred sample size is 100 mm x 100 mm or slightly smaller. The maximum size is 300 mm x 300 mm. Only 1 sample is needed and it is optional to provide additional samples as the backup.
Listed in the table below are the standard NFRC winter and summer environmental conditions:
| Environmental condition | NFRC winter | NFRC summer |
|---|---|---|
| Outdoor air temperature | -18 °C | 32 °C |
| Outdoor wind speed (convection) | 5.5 m/s (26 W/m2K) | 2.75 m/s (15 W/m2K) |
| Outdoor sky temperature | -18 °C | 32 °C |
| Outdoor sky emissivity | 1 | 1 |
| Indoor air temperature | 21 °C | 24 °C |
| Indoor convection | ASHRAE/NFRC inside model | ASHRAE/NFRC inside model |
| Indoor room temperature | 21 °C | 24 °C |
| Indoor room emissivity | 1 | 1 |
These are the standard environmental conditions defined in the NFRC standards and widely used by the industry. It is possible to define local environmental conditions and use them in a specific region.
In the US, the NFRC winter U-value is used (called U-factor and with the imperial unit).
In Singapore, the NFRC summer U-value is typically used, and, in our test reports, both the winter and summer U-values are reported.
For most glasses, the summer condition U-value is smaller than the winter condition Value. The main reason is that the outdoor wind speed in the summer conditions is lower and it results in a lower outdoor side convective heat transfer rate.
We’ve just upgraded our online glass U-value, SHGC & shading coefficient calculator to V2.1.0, with the feature of argon gas concentration specification added.
It is now possible to vary the argon gas concentration to study its impact on glass U-value. The default argon concentration is 95%. Please click the screenshot below to access this online calculator and also read this article on the relationship between gas fill and double glazing unit (DGU) thermal performance.
We are often asked, “can the SRI of my material pass the requirement?”. This post aims to answer this question.
There are no universal acceptance criteria for SRI. In practice, there could be 3 types of acceptance criteria:
There might be other types of acceptance criteria depending on your objective (e.g. if you want to certify your products under SGBP Certification, SGBC has their own requirements).
Please check with the buyer (e.g. architect, consultant or owner) for the project-specific SRI requirements.
Please refer to this page for the requirements in LEED.
Please refer to this document for the requirements in Green Mark (please search “SRI” in the PDF document).
The information listed above may be outdated. Please check with your LEED or Green Mark consultant for the latest requirements.
Additionally, 3 SRI results are presented in our test reports (low-wind, medium-wind, and high-wind, as shown below). If it is not explicitly stated in the requirement, the medium-wind SRI result shall be used in the evaluation by default.
We’ve just released our Q2/2022 OTM Insights newsletter, with the main article “Optical property testing for IGDB / CGDB submission“.
Please click the image below to read the newsletter. For the past issues, please proceed to our branding & publications page.
