I'm sure such an idea would be cost-prohibitive for all but the richest gardener, but I'm wondering if such a thing is possible or has been done.

Using a photochromic glass (like used in self-darkening eyeglasses) for a greenhouse? Maybe even just on the roof panels. A glass that would darken on it's own at high light levels to reduce heat/light inside the GH.

This could be a more automated alternative to shadecloth that wouldn't reduce light levels at times when it was unnecessary or undesired (without having to have a system to draw back/remove and reinstall the shadecloth) such as during times of low sun angle or cloudy weather. Or it could just be appealing for the "not having to mess with it" factor.

Even a "thermophobic" glass (that darkens when a certain temp is reached) if it exists could do the same thing.

Say when light levels reach a certain lux level, the glass would darken to the equivalent of a 60% shade cloth (or whatever). Or if temps reach 90 degrees F, etc.

Mostly just something I'm brainstorming about - I doubt I'd ever do this myself.

Has anyone seen this done?