The building code has gotten very strict with regards to energy efficiency. Spray foam is applied around all the windows and doors, where ever pipes or wires change floors, and around the band boards between the basement and the first floor and the first floor and the second floor. Where ever two studs are located side by side, they must be caulked between to reduce drafts. We went with blown cellulose because it does a better job than the fiberglass batting. In the upstairs the interior walls are insulated for sound deadening purposes.