Some background: we have an 8x8x8 coop made of plywood and 2x4's. Deep litter method with shavings and a deep top layer of hay. Food and water inside the coop since our chickens refuse to leave it (!). 10 chickens and 2 ducks. We have ventilation at the top in a corner. No drafts. (The coop was pretty rushed) We have a new one we can put together as soon as it warms up. Saturday is supposed to get to a low of -25 so we put up foam board insulation inside on 3 walls, (not the wall with the door yet, we will tomorrow) 5 feet up and covered with empty feed bags. Questions: Should we buy more insulation? Do the whole coop? Plastic the outside? More ventilation? I want to keep them from suffering without a heat lamp, I do not want fire and electricity isn't really an option, any advice is greatly appreciated.