Hi, our coop is really more like a really big run, as it has hardware cloth sides (not solid walls). It does have an insulated roof and shade cloth. We have wood nest boxes, but the chickens have been roosting out in the open since spring and we want to build a warm box for them to roost in before it gets cold (this is in central Texas, it will eventually get cold, but not for long, and not for a month or two). This box will back right up to our greenhouse, and we were thinking of leaving the back open (hardware cloth open @ back to air in greenhouse) for ventilation, and heated greenhouse air. Should this "Box" that we are putting in be a big open box with one long wooden roost in it for them to sit on? Can the bottom be open hardware cloth (like a drawer I can slide out to remove the droppings)? What's the minimum width it can be, for four hens? Thanks for the feedback!