Dont even BOTHER trying to get by without ventilation and an enclosed hood of some kind....cool tube or otherwise. We brushed off our hydro man's advice about cooling and found that 1kw HPS can raise the temp of 12 x 14' room a good 20 degrees F. At one point we had the central air running constantly AND a window ac ALSO running constantly and barely kept the temp under control. A good cool tube and inline fan solved the issue completely.