You are likely still going to have problems. You're right, your biggest problem will be heatloss and heatgain.
The biggest problem is that you are more likely to have just one thermostat and your heating/ac is not 'zoned', which means you cannot control each zone or each room. Your T-stat (thermostat) for your house is probably in the hallway or in the living room, and your a/c system is regulated by that. If you did not run your a/c for say a full day, your temp in the living room (or wherever the t-stat is) might be 95F. The temp in the attic will likely be in the 130F range. So if you ran your a/c, and you set it for 75F, when your living room has dropped 20 degrees, it will turn off. Meanwhile up in the attic, your temp will drop maybe only 15-20 degrees, and your temp will still be well over 100F. You will need to install baffles in your supply lines to adjust the air going to the rest of the house (giving less cold air there, so that your attic has a chance to cool further. Actually the best way to do this is to run a whole new trunkline right from your airhandler/furnace up to the attic, and then have a baffle to let less cold air into the remaining house. It will need constant adjustment, as the different temperatures outside will dictate. It is really not a job an amateur can do. In fact I would not do it at all. I would set up a seperate a/c system just for your room up there. It will be much simpler.
I was in the HVAC biz for about 10 yrs.

SpaceNeedle
SpaceNeedle Reviewed by SpaceNeedle on . Attic setup would this work PLease check out I would like to set up a grow room in the attic from my research the temps seem to be the biggest problem. I would tap in to the my central heating and air supply for the intake and run the exhaust back to the return air. I look at it like adding an additional room to the house, just in the attic. I would first use plywood 5/8 and just screw to the rafters then on the inside possibly sheet rock or use the white/black plastic and the outside put insulation. Do you think my temps would be Rating: 5