We've used a heat lamp in very cold weather every winter before this, but after reading a few stories of coop fires (and seeing the pics of smoldering ashes) where all the chickens died a horrible death, we decided to not supply any heat to the coop this year. We've had some pretty frigid weather here already (way below zero, and that's not counting wind chill). It's taken all my resolve to not run out and add a heat lamp or two. Believe me, I totally understand what you're going through. I've had a lot of encouragement from other BYC members who live in areas with weather similar to ours, who have never used supplemental heat. Long story short, our flock is hanging in there after weeks of very cold weather, and they are looking good. There's lots of things you can do to help them out, without adding heat. I do still fret over how cold my babies are, but at least I don't have to worry about their coop burning down with them in it, and that's a relief.