SeaChick, we wouldn't have gotten this far on the issue without all the wonderful materials you developed and passed on!
As far as the suitability of an Eglu in northern winters, I'd say it's mainly dependent on how much snow falls. If your area gets LOTS of snow, then the coop and run could easily be buried under it.
Snow is a great insulator, so it's not all bad. However, if you can't get the run door open in order to add more food and water, or you can't get to the door mechanisms, then you're in trouble.
I have the run covered in plastic so it stays dry, draft free, and snug. It definitely keeps the run warmer, too. The plastic is also over the Eglu itself in order to keep the door mechanisms ice free. If they got stuck, we'd be in trouble. I close and lock the door of the coop every night, both for safety reasons and to contain the heat inside the coop.
The low-profile of the Eglu coop really works in my favor for the winter. It traps their body heat and contains it quite well. I also have a dog kennel type heat pad inside on the floor. The heat pad is covered with newspaper to keep it clean (although it is pet-rated, so I'm sure if gets poop on it, that's OK), and then the roosting bars are on top of it.
I've been doing a sort of modified deep litter system inside the run and coop using leaves raked up this fall. I've added lots of fluffy, dry leaves inside the coop. I fluff them up and add new leaves as needed. I cleaned out the coop once by pushing the leaves and poop into the run, then raking it over and adding fresh leaves to the run. Seems to work very well and not smell at all.
The girls are doing great in the Eglu. So far, the temps have gotten down into the teens F a couple times and they have been just fine.
