One reason for the very low U-factors of many European windows: their frames include thermal breaks made of cork and insulating foam. This triple-glazed window is made by Optiwin, a manufacturer with plants in Austria and Germany.
Passive Solar House Design for better energy efficiency. (example is for New Zealand) Please be aware that the angles may be different for the area you are located. Angles of the sun for Australia can
▶ Passive House - From The Ground Up - YouTube A highly energy efficient Passive House is being built in Syracuse, NY, as part of the From the Ground Up project, to build affordable green homes in the historic Near Westside neighborhood.