I'm currently bidding out a project on a 4000 sq ft 2 story house with a basement and full attic. This is a complete rebuilding of the heating, cooling and hot water. The house currently uses a 15 year old oil boiler to heat the house with steam. There is no central air conditioning and since I am a new owner I would like to invest in a complete rebuilding of the heating, cooling and hot water as I renovate the bathrooms and kitchen. I expect to be able to run the ductwork to the 2nd floor directly thru the ceiling from the attic above and the ductwork to the 1st floor thru the floor from the basement below (but we shall see). Having spoken to local contractors on the phone (they will see the house shortly) there were a couple of points that stuck out in my mind and wanted to see whether it agrees with conventional wisdom: 1-Do I go with a split geothermal system or 2 complete systems (one for the 1st floor and another for the 2nd floor)? Also, what would the cost difference be (expressed as a percent is ok given the fact that I don't have a manual j calculation yet)? I would imagine that a split system with the main components in the basement and an air handler in the attic would cheaper and possibly more efficient during the hottest and coldest times, but that 2 separate systems would be neater and more efficient during the lighter loads. In this 2nd case, the system in the attic would have it's own well supply. 2-What should my budget be? I am going for the works - full ductwork, drilling, heat pumps, small auxiliary heat (town gas line accessible already), desuperheater, on demand hot water, backup generator. I was guessing $50k given the expensive nature of the surrounding area, but I've been warned to expect 50% more than that, which kind of through me off, but realized that I'm looking at more equipment than most projects since it's a complete rebuilding of the HVAC (ie, generator, potential 2nd system, on demand hot water). On a side note, I'm considering installing radiant heat in the renovated bathroom and kitchens, but since that part is fairly conventional and will probably reevaluate the decision once I see the estimates, let's set that aside for the moment. I will update as I go through the process.