If one wishes to build green, that is, sustainably, durably, and efficiently, the most efficient insulation is SIPs or structural insulated panels, which do not settle, and have 10% of the airflow through a wall as studwall/fiberglass. USDOE studies at Oak Ridge confirm that SIPs are much more efficient. Timber frame buildings in Europe are known to last several centuries, and with modern foundations, insulation, flashing, etc., are likely to last even longer. Timber frames use less wood than stickbuilt frames, and, if they last centuries, think of the savings there as well (sustainability). On average, timber frames with SIPs are costing to heat, cool and power ( 1800 ft. Sq. with heat pump alone in WNC) $50.00 per month year around.