If government would pitch in some money to help with insulation so much energy could be saved. An average home lasts about 80 years (though I wonder about the newer OSB McMansions…) , but builders and homeowners have to calculate a payback over a few years, leaving nations to pay for the wasted energy.
Windows I have a slightly different view on. The main thing is that they are air tight, as the R value of glass is very low regardless of how much technology and expense is thrown at it. The main point is to keep frost or condensation forming in extreme cold, or excessive heat transfer if air conditioning. If serious about energy efficiency, windows should be smaller.
In the same vein regarding energy efficiency, houses south of the snow belt should be built to the same standards to reduce air conditioning costs and increase comfort, the insulation and climate control are just as important.