Why are people using a heat source of ANY kind?
I'm in Michigan, and didn't know what I was doing when I started to raise chickens.
I had 2 chickens from a local farm auction. Their coop was a 5*5*4 dog run. A tarp was placed over it, and bales of straw placed outside all around it. They had a wooden one-shelf cubby to roost IN (LOL). I felt sorry for them come Winter as the weather was quite

. I didn't know anything about heated water dishes, but brought the chickens fresh water in a cereal bowl several times a day. I also put a battery operated lantern in there to help brighten their coop. The batteries didn't survive by morning d/t the cold. Pathetic set-up.
After working a 16 hr shift on the coldest night of the year at -75 with wind-chill, I thought for sure they're dead. I peeled back the tarp, fighting the wind and frigid temps only to discover what one would never expect.

Amelia laid her first egg.
I never use heat, have Much NICER set-ups, and have a small handful warm-weather chickens (Ayam Ketawa, Showgirl silkie (12 yrs old), and an Indio Gigante) not to mention 13 other cold hardy breeds). I use deep litter method, and have plenty of STRAW. Never lost an adult chicken to the cold. Not one