I'm a new chicken owner (just got six 2-week old chicks) and am just about to start building my first coop, so forgive my ignorance. I live in SW Washington, near Vancouver. I have seen temperatures as low as +15 in the winter, but that is rare. +25 is more typical for the coldest winter day. Do I need to insulate and provide heat for my girls, or will building a draft-free coop suffice in this climate? Thanks for the help in advance!