Air conditioning. It isn't really about efficientcy, though that is a concern. The simple fact is Europe doesn't need air conditioning most of the time. It is a

Air conditioning. It isn't really about efficientcy, though that is a concern. The simple fact is Europe doesn't need air conditioning most of the time. It is a major concern in the long term because as global warming gets worse, we will need more air conditioning to survive unless we start burying our homes.