The primary insulation used on this house is Woodfiber and Dense Pack Cellulose (Recycled paper). The walls have 6.25 inches of rigid Woodfiber insulation on top of the standard 2x6 framing filled with insulation giving a total of 12 inches of thermally insulated wall! Not only do the materials chosen have extremely low embodied carbon but they also have fantastic sound attenuation as well as a unique resistance to heat that foam and various other synthetic materials cannot achieve.