How many windows or doors do I need to leave open? 

You should open your windows until the air pressure inside the house is nearly balanced with the air outside. One method used to determine when air is reasonably balanced is to place a tissue paper against the screen in the window furthest from the cooler and adjust the opening of the other windows in the house until the tissue paper stays lightly on the screen. You’ll need 2 Square feet of unrestricted air opening through doors or windows for every 1,000 CFM’s of air produced by the cooler.