Hi, I am currently building a coop (coop means chicken house right?) for my backyard in England. Winter is just starting, the last two years got very cold with extended periods of snow. I have never kept chickens before. The coop is 3' x 4' x 3' (Depth x Width x Height) minimum internal dimensions. I have two birds waiting to be adopted, and will probably get a third in the spring. So two birds will have to manage to stay warm in this thing over winter. And I was wondering what sorts of vents & windows I should be providing without causing it to get too cold. I reading about people using electric lights in their coops over winter to keep their birds laying. But is this only a concern for birds restricted to the coop? I plan to only put them in for sleeping at night, do I still need to make a window/provide a good amount of light in the coop? Also is there a recommended minimum vent size to allow enough air in? A large vent or wire mesh panel could easily double as a window to let light through but I fear this will kill and warmth in the coop.