Grab a copy of Jorje Cervantes' Medical Marijuana Grower's bible. A whole chapter dedicated to grow rooms, attic included. Cost u bout $20 USD. Hope this helps.
My 2nd grow was in an attic. It was a DWC (bubbler) setup. The light was a 400w HPS ran in the PM to lower heat(heat RISES) It worked very well for about 6 weeks until me and my roommate lost our jobs and i had to move out. Never made it to FLOWERING but the VEGGING definetly worked. The fan up there adds additional ventalation plus, if any odors leaked NO BODY would smell it due to the higher elevation of the source! I say go for it NEWBIE! And post pics!! LOTS OF PICS!!!