As to why I decided to go with hot water, it is very simple. I live in the northeast, and the house was built with electric heat. It was originaly intended to be the backup, but when I bought the house, none of the original woodstoves remained. I have athsma and allergies, as does my wife, and in previous houses, we have had troubles with the hot air systems stirring up dust. The question about heat loss calculations are mainly to verify whether the contractor has actually figured out what is needed, or if he is doing a guestimate. The calculations should be fairly consistant for each room between contractors. The loss calculation determines how much radiator (or vent) you need for each room, and will warn the contractor if he has to use high output baseboard in a room to keep everything balanced. Also, I think it was your comment about someone in the family having alergies. If that is the case, do not use unlined fiberglass ductwork if you go with forced air/air conditioning. I have seen many systems (including commercial) that have a problem with mold/mildew growth(due to using the ducts for a/c which fills them with cool moist air) in the ductwork, and it is tough to clean out when it occurs.