yea take the window out put 2x2 exhaust fan in,save window and reinstall when you leave. or investagate the 2 vents see where they go or whats on the other end of them, maybe there is a non working exhaust fan already ducted to them but has burnt out,and needs fan replacement, if not se if you can add some duct and a fan to them, but really you should build a small room within the garage for better enviorment control for growing.