If you do some searching on some of the past threads here, you'll find lots of ideas and methods people use that work. It's a subject that has come up a lot.

Also, make sure your coop is snug and free from drafts, which can actually do more damage to your birds.

Velvet ~:>

We are in Z4 and had a very frigid winter last year. Our chickens are large breeds so that helps them keep warm when they roost at night. Also, we insulate the outside of the hoop house with bales of hay that we stack three bales high. In the spring those bales are partially decomposed and makes wonderful mulch for my perennial and veggie gardens. The top of the house is covered with tarp and we open both the front and back doors only during the day.

When it was very cold last winter, we only opened the front door which wasn't too good because there was no cross ventilation. They free range and we were surprised that even in the coldest weather, they spent lots of time outside. Unfortunately, some had a bit of frost-bite on their combs, but it didn't seem to bother them. We have a water heater that just kicks in when the water temp gets below 35 and shuts off when it gets above that. It only ran during the below zero temps in the double digits.

I wouldn't worry about a heater inside the coop at all and think it could be a fire hazard with the bedding. (BTW, we don't use any sort of lighting --- we figure the hens need a break from egg laying in the winter.)

I think your bales of hay are a good idea for winter and for mulch. I do a lot of things like that too. I may have to be away just for a few days when the weather gets really cold and I know I will worry about them. Probably more than I should but, all my animals are my furry or feathered children.

I use my bags of leaves outside the coop for insulation..they don't rot,then in the spring I just throw them out with the garbage,or empty them in our brush pile. This way the bags don't get rotten and heavy from being out all winter. Makes a great insulator!
I also have a heat lamp hanging from their ceiling .. it's a red bulb so they can sleep at night and keep warm :)

Chickens shouldn't have any problem keeping warm in 7b. I'm in 5. My birds are out every day that it isn't pouring rain or snowing ridiculously hard. They're watered outside so that they have to get out of the hen house.

Something to consider - if you give your birds a heater in winter what will happen if you lose power to the heater? The birds are going to be very cold because they aren't used to it. Or what happens when a heat light falls into the bedding? I think it's more important to raise birds so that they're ready for whatever cold the weather brings than set them up for trouble.

What breed of chickens do you have? It really might not be necessary to heat their coop at all, thereby significantly reducing the chance of having a fire. I have cochins, orpingtons, plymouth rock and australorp- no need to heat their pen. When it gets in the teens they huddle together to keep warm. I am assuming yours are grown ups? If you have juveniles or chicks you may need a small box with a lamp. Its november and I have chicks in a 4x4 box with their moms, no heat in the garage and no lamp and haven't lost one yet. They are on their 2nd week. As long as they have food and clean water, they should be fine. Tell me what breed you have and I'll help you out if I can, also how many birds do you have and how big is the coop?

I had a heat lamp in my coop untill a couple weeks ago when I went in there and found it laying on the floor. When I picked it up the floor burst into flames. NEVER again!
It was one of the clamp on heat lamp recepticals but I had it very securely attached to the ceiling with baling wire wrapped around the clamp section. It was still no match for birds flying around.
We have another recessed bathroom heat lamp receptacle in the ceiling and I had a heat lamp in that at one time but that one got shattered by a flying bird. For weeks I was worried about which one ate the broken glass. We got lucky that time too.
I give up trying to heat the birds. My great grandparrents never did it and mine don't need it either.
It's amazingly warm in the coop anyway. It's always about 20 degrees higher temp than the outside temp in the winter. Yesterday the exhaust fan actually came on and it's thermostat is set at 70. It was only in the high 40's outside. They throw out a lot of heat on their own. I think as long as there are no drafts and you have some way to exhaust the air out of the barn that they will be fine. Cold drafts are a big killer for birds.

It was 18 degrees when I let the chickens out this morning. It was sunny with a solid sheet of ice all over the ground. Didn't bother them at all -- they came right out and with the exception of egg laying, were outside all day.

I don't know how cold it got inside their coop last night, but their water was frozen solid. (We have a heated base to normally take care of that problem but we were without electricity for the last few days.)

I never heated our coop until last year when our rooster got frostbite on his comb and wattles. It was a bloody mess. He kept shaking his head and the walls and everything were spattered with blood. Looked like a horror flick. We put the red heat lamp from when they were chicks on a timer and that seemed to do the trick. The light put out by the heat lamp was enough to stimulate egg laying again too. Not that that was our goal, but it was a result of using the heat lamp. I just ordered a thermostat controlled outlet to use instead of the timer. I do worry about the risk of fire or a broken lamp though.

I can't remember where I saw it, but the other day I saw an ad for a heater that had an automatic shut off if it overheated or tipped over. It was small, white and compact.

Velvet ~:>