After the concrete was poured, workers hard troweled the top surface of the wall. This helps create a much tighter fit between the sill plate and the concrete to reduce infiltration and exfiltration — air movement in and out of a house.
Nevertheless, be sure to install sill seal beneath the sill plate to ensure even greater airtightness..
The photo below shows a close up of the top of the wall. Notice the two J bolts — one for the exterior 2 x 4 wall, the other for the interior 2 x 4 wall.
As I noted in an earlier blog, I decided to build double 2 x 4 walls because it was considerably cheaper than ICFs and structural insulated panels. I am also very familiar with this technique, having used it to energy retrofit my 2,400 square-foot classroom building. I would have liked to have used straw bales, but they are strictly forbidden in my county due to the fire commissioner’s wariness (and ignorance of the subject of fire safety).
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+.