I can't claim to be an expert, but I have looked into smokehouses as well. I'd agree with you, you can think of smokehouses as hot or cold. The hot type aren't much more than a barbeque smoker grill. They give your food a smokey flavor, but they are really used as a grill for immediate cooking and eating. I was more interested in a cold smoke house where I could hang and smoke turkey, chicken, ham, bacon, and sausage. Wood smoke is forced thru the smoke house, which is really isn't anything more complex than a chimney. The trick is that the temperature is kept in the 90 to 100F degree range so that the meat doesn't burn during the several day smoking process.
Here is a site that may offer more insight:
http://www.canr.uconn.edu/ansci/ext/build_smokehouse.pdf
Good luck!