Yes, it’s straw in bales. Strawbale insulation is tightly packed and 18″ thick. If you’re wondering what the R-Value of strawbale construction is, then it depends on a few things. The density of the straw, how long the straw itself is as well as the moisture content, how well the gaps are filled between bales and other things like how it’s stacked; on end or flat. Strawbale insulation has been studied and tested in some of the coldest places in the world. The R-Value of strawbale varies between studies but is mostly consistent.
The values fall between R-2.38 p/in parallel with the straw and R-3.05 perpendicular to the straw. So if you have an 18 in thick wall, that would compute to 2.38 x 18 = R-42.84 for walls (currently walls require R-19) and if it were R-3.05 that would be 3.05 x 18 = R-54.9. To read more on the R-Value of the strawbale construction, click on the link below.