Problem in California is insane mandated R values for walls. Aerated concrete can meet previous standards. But not the new ones. So it's use is effectively banned.
Old saw about Generals fighting the last war. Energy efficiency standards assume the need to conserve limited supplies for fossil fuels. And the need to not interfere with building large houses for upper middle class people.
Bad thing is R value is a metric designed to upsell insulation. R30 insulation is twice as good as R15, if you're the guy selling it. If you're the guy buying it, not as much.
I run my furnace for 5 months out of the year. Total yearly cost for nat gas is about $600. And my house is a really drafty 1950's era one. So the max that insulation could save me is $600, that's it.
A heat pump and solar installation needed heat my house in the winter would cost about $12000. But actually the heat pump would only run as I mentioned above for 5 months out of the year. So really just to offset the energy, $6000.
Economically high performance insulation systems lose to solar panels.
That wasn't true 10 years ago. But it's true now. And it'll get worse going forward.
When you're building a house, it's not hard to add additional insulation on either side of the framing. Not terribly expensive, either. You also save on the installation of the furnace (and AC) because it just requires very little heating and cooling.
Since insulation is low maintenance, you'll get those savings over the whole lifespan of the house.
Now, if you're in an existing house, it likely doesn't make sense to tear down all your siding and drywall just to add insulation, since you're having to both demo and build.
Old saw about Generals fighting the last war. Energy efficiency standards assume the need to conserve limited supplies for fossil fuels. And the need to not interfere with building large houses for upper middle class people.
Bad thing is R value is a metric designed to upsell insulation. R30 insulation is twice as good as R15, if you're the guy selling it. If you're the guy buying it, not as much.