Cold weather chickens – 8 things NOT to do in winter! Personally, I think over-warming the coop should be ~ the warmer the coop, the colder it seems outside & the harder it is to acclimate to that cold.
Using wood ashes for your chickens saves you money. store them (fireplace ash only, not BBQ coals, etc) and when needed, mix 2 parts ash to 1 part sand for the chickens to do their dust bathing. And guess what? It keeps mites away.