if i was the judge, i'd say the height of a normal residential room is reasonable, say 7 foot or so(forget what the code is in residential rooms)
I've seen (on this site, no less) some pretty impressive "stadium" style grows in a single room with multiple vertically layered bare bulb setups. I'm sure you'd have no trouble supplying even the most dedicated of smokers with a similar setup. 5'x5'x7'? Sign me up!
(I'm self sufficient in a TOTAL growing area of 4x2! and that includes drying! Actual grow is in two (one veg, one flower) 2.01 sq ft cabs.)