Bunnies - and other critters - lodging in a greenhouse

has anyone ever used a green house to allow rabbits - even chickens, ducks, etc to roost? I was thinking that, in climates with large drops in temperature at night, the body warmth of the animals might keep the temp in the gh more stable.

It is very "permie" to house chickens and other poultry/fowl in greenhouses for the warmth and the CO2 they offer. I suppose rabbits would do the same but I'd not house the rabbits in the greenhouse during the summer. Rabbits do not like it hot.

Mollison suggests chicken heated greenhouses in the big black book, Permaculture.
He speaks of a large greenhouse in Kentucky growing mangoes and heated by five hundred chickens. He speaks of it in rather amazed tones, as this was Much larger scale than he ever contemplated.

At the farm in VA where I worked last year, they had a hoop house not unlike a greenhouse where they wintered the chickens. Even in the snow, it was warm enough to unbutton your coat and the chickens seemed more than comfortable. Another idea I have heard concerning heating a greenhouse is to compost inside it. If you had enough space, you could create a large pile of compost and either fence it off from the chickens or let them have at it.

We winter our hens in an end of our unheated hoophouse. They get the run of the garden on clement days. On snow days they decline to go out. It's mostly for my convenience, not having to deal with the snow and mud, but they seem to like it. The worst is the transition day from summer coop to hoophouse. Change is hard. I don't know that 11 hens can make that much CO2 difference in 1000 square feet.

Sorry for brevity. Must conserve interspace.

Chickens + Winter + Greenhouse = Awesome
Chickens + Winter + Greenhouse + Compost = Awesomer
Chickens + Winter + Greenhouse + Compost + Hot Water + Food-scraps + LEDS + Eggs = Awesomest

BTW, it is crucial if you do this and the animals don't have outdoor access to provide some shade. Unless you have a super fancy automated venting system. It can easily get above 80 in ours on a blue sky day. Panting chickens isn't pretty. It doesn't have to get even close to that before they are seeking shade if the door isn't open to the outside, more like 40-50. They do live in feather pillows after all.

I go in and think "mm 60 degrees isn't it nice" and they are thinking "open the bleeding door, we're dying it's so hot in here" which is another lesson on why it is bad to anthropomorphize animals-we just get it wrong.

Could one perhaps keep the chickens and/or rabbits down in the... what is it called, the term slips my mind atm... the pit dug in the floor to draw down the cold air? perhaps with an exit to the outside for air/exercise.