my hood has a tempered glass plate ... besides being necessary for a fan-cooled lamp, it is a Safety issue, to protect you and your house from a blown lamp ... MH lamps can be really nasty, if they crack ... they can continue to function, while putting out lots of dangerous UV rays ... there is some truth to the idea that the glass absorbs some amount of light, but the safety is more important to me than a few lumens ... :smokin: