You should really think about running water up there. I have an attic grow room that looks very similar. Here I will throw up some pics.
Here is the room after I put in the insulation
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This is an ac vent i put in I just used the one that went to my bathroom. I also now have a cool air intake from my bedroom closet that I have hooked up my lights to.
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My water line... This is so much better than having to log up water its a total lifesaver. I now have a hose and water wand connected to it.
I put up foil faced insulation board because it was much easier to handle then drywall by myself .
I also put white plastic over that recently because I was getting some air leaks so I used spray adhesive to attach it and it worked like a charm.
Here is a pic of it up and running (week 1 of flower) I have 1600 watts in there I also added a pond liner to my floor because the thinner plastic I was using kept getting holes. The pond liner is the shit I could flood my room now and not have a problem.
Anyway I have ran this room for a few runs now both in summer and winter and it stays about the same temp as the rest of my house. I also plan on doing another room almost just like it on the other side. If you have any questions feel free to ask since I have pretty much have ran though all my kinks already.
and good luck