Summer electricity bill in Texas for my previous 1600 sqft house, about $100-$150 month for cooling from Texas ambient to 74 F.
For our new 3200 sq ft house, we cool to 73 F, for the same cost!!!!
That is the difference between a late 70's house, and modern construction, which is foam-filled up the wazoo.
You also mention foam filling, and by proxy, sealing. Many high efficiency homes achieve their efficiency by becoming effectively Tupperware® containers. Which isn't good for the occupants (unless living in Mordor is a goal). Air exchangers are required, muting the gains on efficiency.
God not this again. Active ventilation in 2015 (actually, in 2005) has heat exchangers that recoup most of the heat and do not nearly negate the efficiency advantages and improved comfort of a sufficiently air-tight house. Please review all the literature from the last 20 years which will tell you exactly this.