The inside is open at the top which makes it well-ventilated during the warmer months and the chickens love to roost there, but will be very drafty come winter. We are very concerned our chickens will not be able to stay warm this winter due to the top of the coop being open and drafty. 
When it rains hard water does get into the nesting boxes. This was a very cheaply made chicken coop hence why it is so inexpensive as far as coops go. I learned my lesson.