Heat control w/ growbox in garage

Hey all. I am building a 6'x4'x6' room in my garage. My main problem right now is keeping the temperature in my grow space in the desirable range. The temp in the garage will range from 80 to 90 deg. My initial thought would be to steal some cool air from the house by ducting through the attic and making a small hole in the laundry room and put a vent cover over the hole so it is not too noticeable. Anyone see a problem with this? Would smell be a worry? Once I get to the flower stage, I will have a carbon filter. Will this prevent the smell from coming into the main part of the house when my intake fan is not on, or should I just keep the intake on all the time? There would be about 25' of ducting from the box to the hole in the ceiling in the laundry room. How strong of a fan would I need to produce an adequate amount of air to cool my area? Any other ideas are welcomed, as well as comments or suggestions on my idea. Thanks in advance! Happy growing!

I have to put my steathly grow box in my garage. It is a actech box ($3500.00!)with LED so not that worried about heat other than temp. in the garage. Thinking about ducting house air into the garage to cool and heat a bit.Insulated other than the door.