Not all shipping crates are created equal. I have found some out of osb board that are not worth the effort and others that are very well built requiring only a few structural reinforcements, roofing and windows for ventilation. In many parts of Arizona and southern California a three sided coop works great and minimizes the need for windows. In fact I don't usually have any.
The best value is often in containers in the 7x7x5' range. I got several for 50$ each. I can justify that just as a seasonal coop for my turkeys and young chickens that will mostly be culled. Then I do no modifications other than those for predator controll. If unusual winds or rain happens a couple of old beaten up heavy duty tarps can do the rest. Sure beats building heirloom quality coops that will sit over the winter when flocks are cut back. Also a great way to be green. Some of the better crates I have were reinforced with "free Scrap lumber" off of craigslist and are surprisingly strong and durable. Ugly though LOL.