You need an air cooled hood if you don't have one, otherwise you will never be ok in a space that size. As far as the humidity when the temps go down the humidity will go back up, or get a humidifier they are cheap and work very well.
Even with an air cooled hood you could have some trouble... I recommend bypassing the hood and opting for a portable air conditioner if you can afford it. At least then you'll be at a good temp, and wont lose any lumen's from a hood.