I was very concerned about a power outage too! We have OLD power lines. We regularly have flickering power. I'm building a new 20x10 coop and planned on insulating the walls and the roof. The insulation panels were really very cheap so I figured why not. I was planning on adding two vents on opposite ends at the top of the roof line for winter ventilation, although I do remove droppings daily and don't leave the water in the coop, so any moisture just comes from that night's respiration and defecation.Roosters with big single combs and wattles definitely can have issues with frostbite, especially if the coop isn't well ventilated and gets damp. Heating the coop is tricky, though, and heat lamps, if not very carefully set up, can cause fires. And in a power outage, your birds will have lost their heat, also not good.
Insulating the roof, if it can be managed without giving rodents a nice home, does help with summer sun, and somewhat with winter cold.
Mild frostbite on the comb tips heals pretty fast, and is a minor problem.
Here we don't keep roosters with large single combs and big wattles, and our few single combed hens haven't had frostbite issues in winter.
, with no heat in the coop.
If you decide to use a heat source out there, make sure it's well protected and that the coop is wired safely, it's not possible to be too careful about it!
I'm using foamboard insulation, which came on the ceiling with my current coop (Amish built and too small) and I've had no issues with rodents. What I have had issues with is carpenter bees! This time I was putting insulation in the walls too, but covering it with 1/4" plywood. I didn't think the plywood would be an issue since the coop itself will already be made with plywood. My reasonings are several fold: 1) in the summer, we will have weeks of 95-100 degree weather, and even with all the windows open and a partial shade tree, my current coop will reach daytime temps of 120+. It's insane. I'm actually planning on tinting the windows of the new coop, planting taller shrub evergreens around it (which of course will take a few years to get established), but I was hoping in the mean time the additional insulation will help fight off the heat..... but of course it will also hold heat more! Honestly though, it won't be too big of a deal for us to remove it. We have other projects for which we could use the insulation.It sounds like your new coop will need more ventilation; post sketches if possible. And about insulation; it's nice in the roof, more for summer sun than winter cold, but be very careful about any that you use. Chickens will eat any exposed insulation or insulation board, and rodents love to chew into it and live there.
Keeping the insulation rodent free and safe from the birds and hornets is really hard! We failed here, and had to tear out the wall insulation to defeat the rats and mice, who loved it.