We live in an old house, four levels with a gas furnace. I am thinking of putting in central air, but wondering how I would put in the ductwork. How can I get started on such a project? How should the ductwork be run, what's the best duct to use? Would a heat pump make sense to assist the furnace in the winter time and provide central air in the summer? I am thinking the heat pump could put some heat in the basement where it is pretty cool right now. Thanks,