I don't know if I would use the hvac on the cooltube unless you only use a/c and no heat. You don't want to blow hot air into that cooltube in the winter. You might run one of the ducts close to the wall of the cab/room you are building and then just have an intake for the cooltube in that wall. Just a thought.
Thanks for stoppin by my grow. My leaves aren't gettin any worse so I'm not gonna worry. I think I'm only 2-3 wks from harvest anyway.
Keep in touch.