Has anyone tried a sun shield?

I am thinking of getting one of these to cool my HID lamp in my closet. Has anyone tried it? Opinions one way or the other?

Sun Systems - - Sun Shield- Cool Sun 6"

it says ...'to be used with an air-cooled hood'...(might be useful on a 1000 watt HID light)...other wise a waste of money...IMO.

Thanks, Dutch. I think I don't really understand what an air-cooled hood is then...I have a sun system lamp to which I have rigged up an exhaust vent and fan. I guess that isn't it, though. I was hoping this would "seal" the heat into the lamp so-to-speak, so that my exhaust was working more effectively.

Basically, I am trying to find anything that will cool my closet down.

Thanks for your advice. Would you mind to explain what an air-cooled hood is? I'm new here... :)

PS, I'm running a 250 HID light.