Bruce has already mentioned the need for adequate ventilation, but I'll add a little bit to it.
The usual recommendation is one square foot of ventilation per large fowl chicken. I'm not sure how big the window is that is seen through the doorway but I'll guess in the neighborhood of 2'x2' which would be enough ventilation for four chickens. The ventilation that you currently have below the eaves, at 1" height, will be sufficient for one chicken every twelve linear feet of eave length...for example, a 12'x12' building would yield four square feet of ventilation area with this size of vent (1")...enough for four chickens. Your coop looks to be about 6'x8'ish in size so I'm guessing the eave vent will yield adequate ventilation for two chickens, on a stretch...three chickens. We're up to ventilation for seven (at the most?) chickens. Remember, too, that this ventilation should be permanent...never closed. It also should not create drafts that hit the chickens thus vents located above their heads are the best. Building "tight" coops with little ventilation is one error often made by well-intending people...it makes sense to us but it is counter productive. Respiratory diseases and frostbite injuries are very often directly related to coops that are too "tight". Chickens exhale a great amount of moist air, being as they don't sweat as we do, but regulate most of their body temperature by breathing and to a smaller degree through their comb, wattle, and feet. If the coop is so tight that the moisture can be removed through air-exchange then it becomes very humid which is bad on the respiratory system and can easily condense and freeze on the coop interior and the chickens themselves causing frostbite. As Bruce said, proper ventilation is important no matter which season it is...summer or winter. Really, the only difference in the summer is that they can use much more ventilation than the 1 square foot per chicken and they will appreciate a breeze blowing on them during the hot periods. Is the window we see through the doorway the only window or is the large window that you mentioned a different one on the back wall?
I can't remember who said it, but years ago a highly respected chicken grower stated something along the lines of, "The best chickens come from the leakiest coops." Meaning the coops that had cracks and gaps in them that let lots of fresh air in produced the healthiest chickens. It might have been in PT Woods book where I read that. Here's a link to his public domain book that you can read online...it's a really good read.
I can't really tell from the photo, but do you have a floor in your coop or are you going to be using a dirt floor? You mentioned removing blocks for cleaning....makes me think dirt, cool. If dirt you might want to come around the perimeter and add an apron of some 1/2" hardware cloth (will exclude rats) or 2x4 welded wire (will not exclude rats but will stop bigger critters). If you decide to let the coop be in a permanent position then you could go ahead and bury the apron.
You may want to think about a small run in the case that you have a need to keep them penned up for a few days....maybe for the sudden arrival of a predator or whatever.
The door....gonna put the ability to have some ventilation in it?
It's looking great and I look forward to seeing it with chickens in it!
Best wishes,
Ed
