I have 4 hens in a 4x4 coop, and mine use it only for sleeping and laying. I started with 5in this coop for about a year until one of the hens passed. There was a lot of fussing and jostling about for months when there was 5 in there and one of the girls chose to go back to the small intro coop to sleep instead. So I have a hard time seeing 6 being happy in that size coop. I agree that that you need top level ventilation, the open windows will be great for hot dry weather, but when it cold and damp, and those widows are closed, it will quickly become too humid inside the coop. I'd recommend a much bigger run if you can't let them roam the yard without supervision. Most chickens can get over a 5 foot wall easily, just FYI. Some breeds better than others. Good start, do you have your chicks yet?