I first just want to thank everyone that has contributed to this site. I've found so much useful information for getting started as a grower. Now on to my problem...

I'm am constructing two 4' x 4' x 8' grow rooms in my attic. One for veg, the other for flower. I have my water, light and exhaust systems figured out. My concern is having a cool air intake. The attic can get pretty hot (I live in Texas) and I don't think I want to be blowing hot air into my rooms. What I'm looking for is a solid method to maintain temperature/humidity. I have access to my AC air ducts that I can leverage if need be. I'm also open to using standalone AC appliances. It looks like my only options are:

1) Extend a couple of 4" air ducts from my existing AC ducts to my grow rooms. (some kind of junction connector?) Then just let my central AC unit handle the job. The only downside to this is that I can't regulate the temp independent of my house.

2) Buy a standalone AC unit to install into/onto the grow rooms. I don't want to spend a ton of cash on a portable ac unit if I don't have to.

3) Let the exhaust blowers do all the work and hope it's enough to maintain a relatively constant temp.

Any suggestions for this type of setup?