here is how i have my attic setup

pic 1 is the two vents i use for intake. the left vent is the bathroom exhaust fan that i run 24/7 which is an itake for my box. the one on the right is the a/c vent. i have d/c'ed that duct from the a/c unit and its not connected to anything.
pic 2
the a/c line running from my a/c to my box is the silver insulated one. its bungeed to the a/c unit and sealed with some sort of foam sealant that i cant really remember the name of right now on both ends.

pic3
the pink insulated duct is exhaust that the exhaust fan that came from the bathroom that i am using the intake as an intake fan to the box. i use it as an exhaust straight out the top of my house. straight out of the roof.
pic 4
the white ribbed tube is the intake fan from the bathroom.
i have a 2'x2'x6'(length x width x height)
room that flower 3-4 plants in. under a 400w hps and veg under a 400w mh conversion bulb. i keep my house about 70 degrees f. and i can keep the box about 80 at most and 70 during dark periods. as shown in pic 5.
i also have my box insulated on the outside with a thin pink insulation and coverred mostly on top of that with wood. and i have a seriously rigged cool tube
hope this helps lemme know if ya need any more info
bl33b