The muscle=insulation. We have the traditional, but in the background is the latest (and cheaper) version--blown in. It was up in less than one day.
From skeleton to actual walls...amazing. In some ways the house seemed smaller as your visual perception was reduced. Yet to walk around an actual room was cool. Furniture is easier to see in place and you can start imagining colored walls. Sheetrock=1st of many layers of skin!