Hi, I'm a little confused as to how to make sure the coop is draft-free, yet also well-ventilated in winter. Could someone please clarify? Also, I'm building the coop to allow enough room to expand in the future, but to start, I plan to get only 6 chicks. So I'm thinking a 6'X8' or 8'X8' coop that's tall enough to stand in. Will it be harder for them to stay warm in winter if there aren't that many in that size coop? It can drop below 0 deg F at night here in January/February. Thanks!