I'm in Montana, and it gets very cold here, especially with the wind chill. we just had a -10 weekend, now it's 20 - 30 degrees, but still negative temps at night.
FYI, my coop is not heated and has a small 9"x 9" door that stays open all year, with a 3' x 5"x 5" vent on the top side of the coop, they are out of direct drafts and the chickens have bulked up in down feathers.
They huddle together when in the coop, then come out to play during the day.
 
I built a 4x4 coop on top of a 4x8 run, they have full access to the 2+ acres but the snow hasn't melted so they've been staying close to home under the run where their feet are dry and out of the snow.
I did wrap the bottom of their run the other day to give them cover from the wind, I could hear them complaining. 
 
As for my pvc watering system it's frozen right now, Lol, I really thought I had the winter water problem solved with the heat tape and mass insulation.
The dog bowl for now has been working great, but it needs cleaning daily. The chickens are at my Daughter's house just outside of town, I live in town and try to get out there at least every other day. Hence the reason for a watering system.
 
With all the great idea's that everyone has shared here on BYC, I'm thinking of hanging a 2.5 gal bucket with a submersible aquarium heater in the coop so that the water stays clean, at least for this winter.
With the submersible heaters and d-icers I think that along with the heat tape, it's worth a try on the watering system, of course have to wait until the pipes defrost in spring.
 
The watering system is a 3 in thick pvc pipe that reduces to 2 in, there's an elbow that turns into the coop (3 nipples) then down about a foot with another elbow providing water under the run (4 nipples). it hold 5 Gallons of water and worked great during the summer.
 
I thought the heat tape was going to work, someone said the 3" pipe was maybe to thick for the heat tape, with the exception of the 2" pvc that goes into the coop, majority of the pipe is exposed, the drip from the watering nipples froze before the water in the pipe did so the chickens couldn't get any water out anyway.
 
I haven't seen my chickens eating snow yet, but that's what I was thinking they'd do if they were thirsty.
My problem now is keeping the eggs from freezing... 
  by the time my daughter gets home it's late or I get out there, they've froze.
I have nesting boxes with pine shavings, maybe I should use the heat tape (since it's not working on the pvc) and wrap it around the nesting box??
 
Any ideas?