Seems like the best available today.
For cavity wall insulation, dense packed cellulose is a carbon negative option currently widely available.
https://www.huberwood.com/zip-system/insulated-r-sheathing
And if you are building a new custom home, you'd be crazy not to surpass code for insulation, given the operational energy savings.
Matt Risinger has some nice videos on examples of doing that on his "Build Show" channel on YouTube.
For cavity wall insulation, dense packed cellulose is a carbon negative option currently widely available.