Acceptance criteria for solar reflectance index (SRI)

Related services Solar reflectance index (SRI)

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).

Project-specific SRI requirements

Please check with the buyer (e.g. architect, consultant or owner) for the project-specific SRI requirements.

USGBC LEED SRI requirements

Please refer to this page for the requirements in LEED.

Singapore Green Mark requirements

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The information listed above may be outdated.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.

KSJ MG6-F1 gloss meter

Related instruments KSJ gloss meters

For general applications, KSJ MG6-F gloss meter is recommended. Listed below are the key specifications:

  • Angle: single-angle (60°)
  • Range: 0 – 199.9
  • Resolution: 0.1 GU
  • Beam size: 10 mm × 20 mm

More information is available in the following documents:

For more details, please expand one of the blocks below.


The gloss meter uses 1 piece of AA-size battery. The typical battery life is around 58 hours (alkaline battery; without backlight and BlueTooth).

Basic operations

There are just 3 simple steps to perform gloss measurement:

  1. Power on
  2. Calibration
  3. Gloss measurement

1. Power on

Long press the “ON/OFF” button to switch on the gloss meter

2. Calibration

There is a calibration board in the base holder of the gloss meter (shown above). Mount the gloss meter to the base holder and buckle it properly.

Short press the “Calibration” button. While the “CA” symbol is flashing, short press the “Calibration” again. The “CA” symbol disappears and the gloss meter is calibrated.

3. Gloss measurement

Take out the gloss meter from its base plate. Attach the measurement port (at the bottom of the gloss meter) to the surface to be measured. The gloss result is displayed on the screen, without pressing any button.

Good practices

The following good practice practices are recommended:

  • Keep the calibration board and the lens in the measurement port clean.
  • Re-calibrate the gloss meter frequently.
Smartphone controlled gloss measurement

It is possible to perform online gloss measurement with a smartphone (both Android and iOS) via BlueTooth connection and store the gloss measurement results in the smartphone.

Refer to the user’s manual for the details.

Can daylight reflectance be tested with ASTM E903 only?

Related services Daylight reflectance

As suggested by the title of ASTM E903:

Standard test method for solar absorptance, reflectance, and transmittance of materials using integrating spheres

ASTM E903 is for the testing of solar absorptance, reflectance, and transmittance, but not daylight reflectance directly. The procedures of spectral reflectance measurement with integrating spheres are described in ASTM E903 in detail, but it is still insufficient to get the daylight reflectance results with ASTM E903 only.

Therefore, at OTM, ASTM E903 is supplemented with other test methods in daylight reflectance testing:

  • For general materials: ASTM E971 and CIE 130
  • For glass materials: NFRC 300

Please refer to our daylight reflectance page for more information.

Small and light class C pyranometer: LPPYRA-Lite

Related instruments Pyranometers

Delta Ohm just released a new pyranometer product LPPYRA-Lite with the following features:

  • Spectrally flat class C according to ISO 9060:2018
  • With thermopile sensor
  • Output type: mV (default) or 4-20 mA (on request)

The weight of the pyranometer is only 150 g. It is suitable for small PV power plant monitoring or general solar radiation measurements. Please click the pyranometer photo below for the datasheet.


How to get window film optical & thermal properties with different glass substrates?

Related services Glass optical & thermal properties

Typically, window film optical & thermal properties are tested with 3 – 6 mm clear or low-iron glasses as the substrate. Window film properties obtained with such high transparency glass substrates are more appropriate for product performance rating purposes.

In real buildings, window film products can be attached to all possible glass substrate types, such as tinted glasses, low-e coated glasses, laminated glasses, and double glazing units (DGUs). There are two methods to get window film optical & thermal properties with different glass substrates, as described below.

Option 1: direct physical test method

With the direct physical test method, the window film shall be attached to the actual glass substrate to be used. The whole glass system with window film is tested as usual.

This method is recommended for most applications, with a small number of glass substrate types.

Option 2: physical test + calculation method

With the physical test + calculation method, the following glasses need to be tested (based on the NFRC 304 method):

  1. Window film on a reference glass substrate (typically a 3 – 6 mm clear or low iron glass)
  2. The reference glass substrate (without window film)
  3. Other glass substrates

With the test results of glasses 1 & 2, the window film only optical data can be calculated. The window film only optical data can then be added to all glass substrates tested in step 3 to get the combined glass with window film optical & thermal properties.

This method is recommended for product development applications, with a large number of glass substrate types.

On-site measurement of wall system U-value

Related services Thermal conductivity, On-site testing & monitoring

We are now able to test wall system U-value on-site. The test method is based on ISO 9869-1, with some improvements for Singapore’s environmental conditions.

The measurement instrument setup is illustrated below:

The following 3 quantities are measured:

  • Indoor side wall surface temperature (by a temperature sensor)
  • Outdoor side wall surface temperature (by a temperature sensor)
  • Heat flux through the wall (by a heat flux sensor)

The instruments need to be deployed on-site for a few days. The thermal resistance (R-value) of the wall system is calculated from the averaged results. The thermal transmittance (U-value) of the wall system is calculated from the R-value and the surface film resistances defined in the BCA ETTV code.

For better measurement accuracy, a surface electric heater of the size 0.5 m x 0.5 m is attached to the indoor side of the wall system to increase the indoor/outdoor temperature difference across the wall system.

Color measurement instrument calibration service

Related services Color & color difference

We are now able to calibrate color measurement instruments (e.g. tri-stimulus value color meters or spectrophotometers) with 8/h or 8/d geometry, with the following steps:

  • A set of color tiles (12 pieces, shown in the photo below) are used.
  • The color tiles are measured with our benchtop UV/VIS/NIR spectrophotometer.
  • The color tiles are measured with the color measurement instrument under calibration.
  • The color differences (between our benchtop UV/VIS/NIR spectrophotometer and the color measurement instrument under calibration) are calculated and compared.