We are building a two-story home (2300 ft^2) in central Missouri with the lower level as earth contact. Exterior walls (9' high) are insulated concrete formed (lower) and 2 x 6 (upper). We are going high end on insulation. We have obtained quotes from two installers of geothermal systems and both suggested 3.0 to 3.5 ton systems. Their recommendations do not seem to differ from those for slightly larger homes with much less use of insulation (also not earth contact) and having much more window surface area. Am I wrong to assume that controlling heat loss / gain from environment can reduce size of a geothermal heat pump required to manage temperature and humidity?