PAR reduction from glass canopy

[Frogspon]

How much does a glass top reduce PAR compared to going open top?

 

[Pistondog]

Depends on glass type, but a reduction of 10% might be estimated from clear glass transmission efficiency. This assumes uniform efficiency across spectrum, which is probably not true.
Maybe post in lighting forum.

 

[JCTReefer]

Effects of various aquarium covers on light transmission

Nice write up, very helpful! I assume that the glass was spanking clean for observed 12% reduction. Any chance you used glass that has some salt spray on it for "real" life situation?

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