Not exactly sure. I've just got one of those crappy plastic greenhouse things but I kept a some asturian tree cabbage's in there over winter ok with the door closed. But I made covers to go over them by making a vertical tube of plastic mesh covered on the top and round the sides with fleece that sits just inside the inner edge of the 30 litre tree pots they're in. I don't think they grew much but I did'nt water them at all really Incase it chilled them so they may have been a bit dormant. They survived no problems.
They have been fine this year with a bit of water now and then and they've grown a bit as well. I just left them under the covers to keep butterfly's off and I've eaten some of the lower leaves, no eggs or bugs or anything. They are on a wooden board that's raised up a bit off the ground though as well.
Only thing apart from temperature I'd think about I suppose would be the reduced daylight hours for some plants.