To get really high R value on insulation, often that means a 2x6 or 2x8 framed outer wall to allow for the additional thickness needed by the insulation. Double

To get really high R value on insulation, often that means a 2x6 or 2x8 framed outer wall to allow for the additional thickness needed by the insulation. Double pane windows are well-surpassed by those with many panes and carefully designed frames with low thermal bridging. Aside from more insulation you need great air sealing, across every joint and in every window and door frame. Older construction had no explicit ventilation, just a lot of leaking such that the house "breathed". On modern, efficient homes, the air seal is very tight for efficiency reasons, so you need an ERV/HRV system to exhange air for you to keep the air healthy, while minimizing energy loss for that airflow. Insulating materials used inside the roof and sheathing are typically closed cell foam or rockwool, or in Europe they sometimes use a wood fiber based insulation. There are lots of caulks and adhesive tapes for getting a good air seal, and there's also a technique where one pumps the house frame full of a vapor that reacts across pressure drops and plugs any holes it flows through. Last, well insulated homes can get cheap heating and cooling from modestly sized heat pumps which are very efficient. One zero energy home I saw has heat exchangers on the roof to capture energy from the sun for warm water as well, supplemented by heat pumps powered by photovoltaics.