"Going green often requires alternative materials for home construction. The Smiths used insulated concrete panels for the walls. These panels help regulate internal temperature so less energy is used for heating and cooling. Architects also adapted a floor system modeled after a design dating back to the Romans, according to Farr Associates. A series of interconnected ducts is sandwiched between pre-cast concrete panels on the bottom, and a layer of poured concrete on top. Warm or cool air is circulated through these ducts to provide more efficient temperature regulation."
"Good green design also incorporates on-site 'materials' -- natural features that can improve the house."