Hi everyone! I have two "flocks" -- three hen in a five by five by four henhouse, and two girls by themselves in a three by two by two house. Both lots have access to large runs. So far they've been fine in this Central Pennsylvania winter, but we're expecting an Alberta Clipper this weekend, with lows at night in the single digits, and on one night -1. I've plugged all holes, and put a thatch of a foot of hay on the roofs. Will they be okay? Should I try to rig a light bulb in their houses? Any suggestion/advice would be appreciated...I love them all dearly! Thanks.