AAC, also known as autoclaved aerated concrete, is a mineral block made from cement, lime, sand, and water. It removes the wall cavity completely, and that changes literally everything.
During manufacturing, a tiny amount of aluminum reacts to create millions of air pockets, which is what makes it super light. By the time it's cured, it's a stable mineral, so you don't have to worry about any off-gassing. There are no glues, there are no resins, and there's no paper drywall.
So the real question isn't whether it's "clean." The real question is how it behaves when moisture shows up.
AAC is porous, which means it can absorb and release moisture, and it does this much more gradually and slowly. Because of that, it can dry easier if, keyword if, it is detailed correctly. Similar to rammed earth, AAC acts as a moisture buffer.
In Japan, they've been building with AAC forever, and they have some of the strictest seismic codes in the entire world, because they have tons and tons of earthquakes and natural disasters.
If I couldn't build with rammed earth, then I think AAC would be at the top of my list of what I'd be looking at if I wanted to build a healthy home.
