Poly Greenhouse as a winter coop??

[jdare]

I am new to chickens, we just raised our first chicks this spring and haven't had to over winter them yet. A light bulb went off while I was walking by our large greenhouse today, thinking how great it would be if the chickens over wintered in the greenhouse and all the compost could just be tilled into the ground and used to grow veggies in the spring.

But my question is, will this be warm enough if we have a few heat lamps? We have cold winters here, not uncommon for -25 degrees Celsius. The greenhouse is large, about 900 square feet, we have about 50 chickens.
Any thoughts on using our poly greenhouse for a coop during the winter?

 

[Eggcessive]

A picture would be of some help. Cold is not so bad as long as it has durable wire or walls to keep out raccoons, fox, oppossums, skunks, weasels, dogs, or other predators. It should get sunlight to warm it in daytime, but not be too hot, and have shade for them.

 

[jdare]

Not the greatest photo, but it gives you an idea. I'm not too worried about predators, as our house is just behind where I took this shot from and we have 4 dogs that roam the property at night....but there is always a possibility I guess. We mostly have the big guys, like bears, cougars, coyotes, skunks too. I'm worried about warmth mostly I guess.