Once the site was excavated, we began by forming up the footer. I did not insulate under or around the footer because I believed it was unnecessary. Although there will be some bridging loss around the footer, there isn’t an easy or short path for the heat to escape. The ICF foundation walls lying over the footer are rated at around R-30; the insulation under the slab consists of five inches of extruded polystyrene (XPS). Its R-value is 5 per inch. The top of the ICF wall was sprayed with foam insulation.
Contributing editor Dan Chiras is a renewable energy and green homes expert who has spent a lifetime learning life’s lessons, which he shares in his popular blog, Dan Chiras on Loving Life. He’s the founder and director of The Evergreen Institute and president of Sustainable Systems Design. Contact him by visiting his website or finding him on Google+.