Visible Light Transmittance
Q: | What is Visible Light Transmittance (VLT)?
|
A: | The percentage of visible light transmitted through the fenestration product.
|
Back to Top |
 |
Q: | How is Visible Light Transmittance (VLT) determined?
|
A: | For flat specular products the VLT can be determined by computer simulation. For products that are not flat or the light transmission is diffuse it is necessary to test.
|
Back to Top |
|
Q: | Can diffuse tested products be NFRC certified.
|
A: | Not at this time, however a protocol is being developed at NFRC to allow this certification of non-specular products.
|
Back to Top |
|
Q: | What outside procedure is followed for testing diffuse products?
|
A: | ASTM E972 is the preferred method of testing VLT for diffuse products. (This procedure is used in conjunction with the equipment described in ASTM E1084)
ANSI/ASHRAE 74 Standard 74-73 also describes a procedure for measuring VLT which is identical to the ASTM procedure. The ASHRAE procedure is in the process of being updated.
|
Back to Top |
|
Contact Us with your questions.