We have the basic coop designed. We got a bunch of free 4 by 8 foot composite wood pieces and we need a new coop for the ladies pretty quickly. It's going to get cold soon, and they need more protection from the elements than what they currently have. So the design is pretty simple. 4 of the boards basically put together with 2 by 4s, the side pieces angled and one side shorter than the other. The top is shingled. We have a full-size door for us to easily have access to the coop for maintenance. On the interior is a 2nd level. We need to add ventilation, a ladder to reach the 2nd level, perches and nesting boxes. How much ventilation do we need? And it does occasionally get into the 20s and (rarely) the teens here. How important is it to have a heat lamp in there? Will their body heat be enough on those days, or is it vital that I also have an area to plug in a heat lamp on those really cold mornings? We're planning on finishing up the coop this weekend and hopefully have the chickens moved in there by the end of the month.