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I have no experience with either the herbal roof or the rainwater catchment. I’ll not comment on the herbal roof, but my thoughts on the catchment center around the runoff being nutrient rich. If you are not filtering it, the rain barrel will fill up with solids. If you plan on some type of automatic watering system, expect it to get clogged. Even if you do filter it, the effluent will have a lot of nutrients in it. I’d expect algae and other growth to form, so you might get it clogged anyway.
Chicken poop is pretty hot from the nitrogen. If used directly on plants, it can burn them. It depends some on the plants and if it comes in direct contact with the plant. It is normally recommended to compost the chicken manure first. You may have this all worked out, but that would be my concern.
The way I understand your climate is that the summers are usually generally mild but you can get some days in the upper 80’s or maybe low 90’s. Winters are usually pretty mild too but the lows can get in the teens Fahrenheit. That’s not too bad for chickens. The heat will be a bigger danger than the cold. As long as they are not in a direct breeze when sleeping, they can easily handle that cold weather. They still need good ventilation in the winter, so just have lots of permanent ventilation over their heads when they are sleeping. In the summers, I recommend even more ventilation. This can be below or at their sleeping level. I’ll give you some links to articles that might help. The ventilation one for sure, but the other two have good information.
Pat’s Big Ol' Ventilation Page
https://www.backyardchickens.com/web/viewblog.php?id=1642-VENTILATION
Pat’s Cold Coop (winter design) page:
https://www.backyardchickens.com/web/viewblog.php?id=1642-winter-coop-temperatures
Pat’s Big Ol' Mud Page (fixing muddy runs):
https://www.backyardchickens.com/web/viewblog.php?id=1642-fix-a-muddy-run
That should be big enough for four chickens. I hate to give hard and fast numbers for how much space you need for chickens because it varies so much for each of us depending in the chickens, our climates, and how we manage them. I’ll just mention the more space I give them, the less hard I have to work. I’d be quite comfortable with your space for four chickens.
Make sure you can walk in the run without banging your head. Also, make sure you can reach everywhere in the run and coop. You may need to clean, gather eggs dropped where you don’t expect them, or maybe retrieve a chicken that does not want to be retrieved.
Inside the coop, all you really need is a roost and one or two nest boxes. I’d suggest two nest boxes although they will probably all use one. The second one is mainly to give you some flexibility, such as if you have to deal with a broody hen. You can feed and water either in the coop or outside. It just depends on how you manage them. If they are locked in the coop during daylight hours a lot, inside the coop is probably best. If they are allowed outside pretty much during all their waking hours, you can do that in the run.
You do have some interesting ideas. It will be fun to see how they work out. Good luck and again,
