A:Answer Hollie,
This device does need to be vented. This AC unit comes with an exhaust port hose that needs to be mounted to the outside so hot exhaust air can escape and the unit's cool air can circulate inside. This exhaust hose has a diameter of about 5 inches. If your garage has any normal sized double hung window this will work perfectly because this AC unit comes with a double hug window mounting kit. If you have another style window you could shop around online to find different mounting kits which I know are out there, and will work for this unit. Hope this helps! Cheers.