Hps cool question - glass between light and plants?

I've seen a lot of pics where people are putting glass between the light and the plant.. does this help keep temps down? this set up would be for a mini cab, would having glass in front of the light allow the plants to get closer to the light before getting too hot?

Thanks

It does keep the heat down which is good. But it also blocks some of the uvB rays which is bad. According to High Times contributor Jorge Cervantes only use the glass if heat is a real problem.

I use a 1000k dual system by sun systems and I have to use the glass on the bottom of the reflector because of a heat problem due to limited head room. I still average 1.5 oz per plant on all my grows. Just my experience........

Don't know if I'm stating the obvious or not but...if you use glass you'll need to use some flex duct and exhaust fan to remove the hot air directly from the light. The reflector I have has a 4" hole on the side just for that purpose.......

I took the glass off of my reflector and it seems so keep temps down more. I guess its because the the heat is not trapped in between the reflector and the glass.