Well, have you ever been in your attic in the summer time when its hot outside? Have you ever been in there in January? If its anything like mine, its about 140F+ in the summer up there, and frigid cold in the winter time.
To sum it up, the attic is a very poor place to put a grow room where you are trying to keep temperatures moderate. Unless you have heating and a/c up there I think its a waste of time and effort. You would be alright if you only used it in the spring and the autumn, but winter and summer is very difficult.

If you want to grow year round up there, I say forget it.

keylime