As someone that has been interested in houses and housing construction for 25 years, the biggest change is on making a house air tight. Specific levels are now

As someone that has been interested in houses and housing construction for 25 years, the biggest change is on making a house air tight. Specific levels are now called for in the building code. The construction industry is still trying to work out the kinks though and unfortunately fixing the kinks requires ever more equipment, complexity, and cost.