Oh i've always been in favor of underground or earth bermed housing. i just haven't been able to afford it. And these days, doing it in ways that would be more energy efficient are easier than ever if you can afford it. As i understand it there are now solar collection panels that can double as windows which means the wiring from them to house shorter and less complex than with free standing roof mounted panels. One could use those for the skylights and any other actually level with or above ground windows. I would also like to be able to clean my stovepipe myself without having to get up on a slanted roof. i just don't trust my balance and footing that much anymore.
Even without solar panels underground houses conserve energy, warmer in winter, cooler in summer. It would not even take that thick a layer. Currently we live in a 170+ year old house the outer walls are a foot thick and there's only one small window facing north and minimal ones facing west (both directions prevailing winter storms come from). Once all the drafts plugged up the interior stays comfortable in winter. (This is a regular fall chores when cools off enough to keep windows closed 24/7/ In summer, despite having no shade trees near the house, the interior stays relatively cool especially our large living room in center of house.
Early morning and late afternoon when sun pouring in peripheral rooms get warmer. Most summers just opening a window on each side of house keeps us cool except during the hottest late afternoon hours on hottest days. This year a little more as we've had more 90+ degree days. And the humidity has been higher than usual. Which means i can feel the cool of the interior when i come in but my body takes a while to cool down and feel comfortable if i'd been out in heat and humidity, especially if doing chores not just running errands.