I'm new to chickens, have 5. One is a yr+old, rest are April 2019 babies. I did buy a radiant heater (purchased at Tractor Supply on sale 29.95, regular 39.95) as we get to -0 frequently through the winter. Putting a sensor by the roosts, so I can monitor the temp of the tractor in my house. This heater is awesome. We just use the low setting as when it gets cold/windy. Which raises the temp 20 degrees, never used the high setting yet. We have a nice tractor, The hutch is not big but definitely a great size for 5 large girls, we also have the underside which is enclosed & what we call the breezeway which I wrapped in plastic to keep the air from going through. My egg production is good. I don't add light, using natural light through windows. I know I'm spoiling them, but I just can't think of them as livestock they're my girls.