Diffuse daylight reflectance of glasses

Related services Glass optical & thermal properties, Daylight reflectance

As discussed in the glass daylight reflectance page, the diffuse daylight reflectance of a glass is negligible, with the following two relationships:

Diffuse daylight reflectance = 0
Total daylight reflectance = Specular daylight reflectance

In the test report, we will report the glass daylight reflectance only. Below is an example:

There is only 1 result, without the separate total/diffuse/specular reflectance components.

If the result above is expressed in the conventional total/diffuse/specular daylight reflectance format, it would be:

  • Total daylight reflectance = 0.088 (8.8%)
  • Diffuse daylight reflectance = 0.000 (0.0%)
  • Specular daylight reflectance = 0.088 (8.8%)

The diffuse daylight reflectance is negligible, but not exactly 0. It is related to the haze level of the glass. The haze level of typical glasses is less than 0.5%. The diffuse daylight reflectance can be calculated as 0.088 × 0.005 = 0.00044 (0.044%) ≈ 0.000 (0.0%)

In practice, the instrument is not able to accurately measure (or resolve) the diffuse daylight reflectance of a glass. The test method of measuring glass diffuse reflectance is also not defined in the standards.

Therefore, there is only 1 result in the test report, without 3 separate components. The diffuse daylight reflectance of a glass can be estimated theoretically, but cannot the determined by an instrument.

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