Last week a few of us went to Urbana, IL to visit the Passive House Institute (PHIUS). One of their members, Ryan Abendroth (who's helped out the likes of Studio 804 and the U of I Solar Decathlon Team) showed us the Dublin House.
It's a very small, roughly 1,000 SF, project built as affordable housing. It has roughly 15-1/2" of insulation in the walls and 10" of rigid foam beneath the floor slab.
Here you can see the thickness of the walls.
It was an unseasonably warm day, but even with the solar gains the house wasn't that warm (the AC was turned off). This is the ERV (energy recovery ventilator) closet. That box on the top left exchanges energy from the geo-exchange loop before entering the ERV. In the summer it cools air and in the winter it warms it. The pump is "intelligent" and learns how to run more efficiently as it gets used to the buildings needs.