Another option over strawbail is hemp. There is amazing potential with hemp for two reasons. First its insulation quality is excellent but it alos holds the advantage of inhibitng mold. Add to that the fact that it is a hardy, efficient crop with long fibre and needs no pest control (pesticides) and you can see the value here ;-)
it is already being used in parts of Europe for insulation, building material (hemp boards) sound baffling, concrete enhancement, etc. It is harder to establish here because of the governemnts extreme regulatory nature.