I have no idea how much it affects the data used to make that calculation, nor how much is its relevance in the US, but here (EU, Italy) besides the building co

I have no idea how much it affects the data used to make that calculation, nor how much is its relevance in the US, but here (EU, Italy) besides the building code improvements there has been a very noticeable increase in amount/complexity of electric and hydraulic/heating/conditioning installments.