It would not be wise to build a green house around your bees. Bees do not hibernate, they ball up and vibrate to keep the queen and brood warm and if you make a green house they will feel that its warm in the hive and want to leave to forage. this is the reason that hives are united and winter feeding is done. I am sorry if that is not
the answer you want to hear but a responsible person would kill all extra queens and or
sell your queens to a poor soul that has lost one and unite multiple hives before losing all of his hives if that was the best thing to do. if you do not know how to unite multiple hives then you must take the time to look up "uniting hives" "newspaper" and "third box" method. It usually takes about 3 to 7 years to get through most of the problems and
experience what to do and not to do with bees. uniting multiple hives can save your bees and allow you to split them back apart later when the hive is larger and stronger and she makes more queen cells.
I do not know your hive or how big they are so you will have to make the call based on information you gather.
Things that will help a small hive:
* Building a wind block around the hive but NOT touching the hive. wrapping hives directly builds up moisture inside hive and will kill bees.
* Uniting multiple weaker hives to make a strong hive
* winter feeding may save a smaller hive to get them through winter.