Welcome to BYC! Please make yourself at home and we are here to help.
Barred rocks are such a great breed! Glad you are enjoying them!
Ventilation is probably one of the most important things to have in winter. Without proper ventilation your birds will get frostbite, respiratory illnesses and other problems.
Chickens can survive brutally cold temps as long as they are dry and out of all drafts. Sealing up all cracks in the coop and putting in about 1 square foot of vent space in the eaves per bird. Wind chills are merciless on chickens sleeping at night so make sure your coop is draft free.
Other things to do to help keep your chickens snug this winter include using straw as a bedding, using the 4" inch side of a 2x4 roosts. I also put a towel that has been in the dryer and put it on the roosts to warm their feet. Make sure that there is no water spillage or moisture collection on the bedding as this can also result in frostbite. On the very cold nights you should rub vaseline on the chickens' combs and wattles to help prevent freezing.
Here's a link on frostbite and ventilation.
https://www.backyardchickens.com/a/frostbite
https://www.backyardchickens.com/a/...-go-out-there-and-cut-more-holes-in-your-coop
You don't need a heat lamp if you have ventilation, proper bedding, proper roosts and proper feed. In the winter you should be feeding your normal layer, grower or chick feed along with scratch as this will keep the birds warm especially if you feed it in the evenings.
Bedding that is warm and absorbent is also necessary. Wet bedding mixed with the cold temps and wind chills equals bad frostbite. So either use straw, shavings or shredded paper. Straw is possibly the best bedding to use in winter. Line the nests with straw to help prevent eggs from freezing. Bales of straw help act as insulation and keep the coop even warmer.
Heated water bowls are also imperative. Chickens drink non-stop in winter and they can't do that if their water is frozen! So either buy a heated bowl or use a heated base on the bottom of their regular waterer. I've also heard of people who place a 40 watt bulb in between bricks and then put the water on top in a bowl. Make sure the waterer isn't plastic.
Good luck and welcome to our flock!