I kicked my chicks out about two weeks ago (two groups about 3 weeks old and 2 weeks old), in my upper pen in the coop with a heat lamp and a heating pad, they're fine. Accidental turned the power off in the coop one night still fine. It was -10 C outside overnight, so between -10 C and zero in the coop, they did fine (luckily). Using a seed sprouting mat in my brooder inside, it's working great, really great for $13. Lol