My BBW hens are six and a half months old and they still shiver. If they sit on your lap, you'll feel just how much heat they loose through their bellies. Try keeping something beneath them that is fluffy and insulating (a good layer of shavings, hay or straw). We use shavings, but of course, they prefer to roost on the porch, where I have to pluck them off and take them to bed every night.