I have friends here in Sweden who keep their Hedemora birds in a barn overnight with no heating. The temperatures up here are often down to -20. They have told me that they just need to make sure the water doesn't freeze. I have an insulated play house with a heat lamp that I'm planning to put on if it gets below 0 or -5. I have one silkie chicken that I'm guessing is not as cold hardy.
I haven't managed to get any of them to sit on my knee yet but if we go out into the garden and shout for Kristoff (the rooster) he crows and comes to find us. Once they see us, they run or even fly over to us. They are really beautiful - everyone seems to love the black combed ones and the silkie feathered ones.
There are genebank chickens where you must have a certificate and I guess they are registered here too. Those apparently can't be hatched by eggs, they are naturally bred only. I don't have anyof those... yet.