I live in Texas close to Houston. My question is: What is too cold for a chicken? I was thinking about closing up the coop vents during winter but I am worried about ventilation. Should I just close the windows on cold nights and then open them during the day? Do they need a heat lamp? These are my first chickens and I don't know what to do. It is only low temps in the 50s right now, so I am sure that they are fine, but I am trying to plan for the winter.