For the last few years we have been building with reclaimed styrofoam tree planting boxes. Lots of tree nurseries have these things lying around in the thousands. Ultimately they are chipped up and put into the landfill or shipped to China to be made into CD cases. We have found them to be a highly versatile building medium and the insulation value is incredible. We've used them for load bearing walls, infill for timber framing and infill for conventional framing (stuffed in between the 2x6's). If you can source them out I highly recommend their use. check out some of the pics on or website.
http://yewlandia.weebly.com/what-were-up-to
