[_delirium]

I’ve seen a few of these. A family friend built a custom energy-efficient house in the ‘80s that is partly built into a hillside. The other main feature is automatic ventilation when exterior temperature/humidity conditions are favorable (basically just automatically opening windows using ‘80s-era home automation electronics). My guess is you don’t see more of these because the site-specific architect and engineering costs put it out reach for non-wealthy people, unless you have the skills to DIY much of it. Plus possible maintenance issues and building code and insurance hassles. Here’s a basic intro from the DoE: https://www.energy.gov/energysaver/efficient-earth-sheltered...