I am building a coop for my chickens and it is 48”x30”x36”. Only problem I’m worried about is ventilation. It can get -20°F here and I don’t want it to get too cold in the coop. It will only be 2 Belgian d’uccles in the coop, so would only a few small holes work? In the past I’ve had coops with 5-12 chickens and no vents at all, so I’m not sure how many I need and if it will make it too cold?