My son is building a home near Waterloo, Iowa. The home will be 1,500 square feet. Both basement and main level will be constructed of ICFs. A preliminary Manual J says he needs about 25,000 Btu./hr. He's thinking about geothermal; radiant heat in the basement and forced air in the living level. From what I have gleaned from many forums is that with a super-insulated home it's more cost effective to go with a tank-less gas fired boiler or a conventional force air system and forget the geothermal. What is the most cost effective and environmentally friendly solution?