So we are now building up the back wall. Curt has to be very hands on with this part, since we are making it out of a fairly new material called Rastra Block. It's mixed up cement and recycled styrofoam cups. So the walls already have the insulation in them. It has a very high RA value. Since not many people have worked with it in our area, Curt and another guy R.J. who we were really lucky to find since he has built a rastra block house before are putting up the back walls. Here is the last time Mom was able to see the progress. There she is watching Curt putting up walls.