We have the very same chicken house! we've only had it a few weeks as their last home a secondhand shed was well past it best.
Our are free to range the a garden (veg plot fenced off), they even come in house most mornings, wanting some food. They jsut walk past the dogs without a care?
We haven't lost a bird to a fox since the hunting ban, and we back onto fields. A couple of local go out shooting them, weekly, however my friends with urban chickens are not so lucky-killed if not locked up at night! Ours haven't been locked up for years, just come and go as they please. Very low maintanence.