thanks for the quick replies guys. the closet is about 3' x 3' x 9' high (possibly a little wider/longer, but from memory this is my best guess). he cut a hole in the ceiling of the closet and is putting in a fan, which extracts into the attic. the problem with ventilation is, there is no intake. i thought maybe cutting two holes, one fan blowing cool attic air in, the other blowing out...? he is set on using a HPS, but i know how hot HPS get. Could you further explain the 'cool tube' cooling idea?