I did this exact thing nearly. Check out my link in sig. The only issue I've ran into was heat from my AC heating up the garage. Gonna build an exhaust for that to push that hot air out so my dogs can chill in there in summer time. Also pointless to heat air your pulling into your room to try to cool down. I pull air from my garage only had to cut one hole for exhaust. Put a small intake into my veg then a passive light proof vent from veg to flower where it gets scrubbed and taken outside. I really would recommend venting that air outside anyway you can. I did two rooms an 5x10 with two t 5s for veg and an 8x10 flower room with 2 1000 watt hps lights. If I would do it again i might build it just a tad bigger to have more room in the flower room.