Straw bale construction isn’t hay, and its characteristics will probably surprise you: https://www.familyhandyman.com/article/straw-bale-construction
Straw bales have up to three times the R-value of conventional home insulation, along with excellent soundproofing and fireproofing characteristics.
You got me properly, I was wondering where you were going with all that by “selective breeding” and quite happily read all the way to the end in order to find out.