Underground housing, underground businesses, etc. Would that be better for the environment + possibly save on energy costs? Also possibly safer in certain scenarios like tornadoes etc.
Potential issues that immediately come to mind are ventilation, earthquakes, and flooding. But it’s not like underground dwellings/basements/etc. aren’t a thing, so maybe those issues have been addressed in ways I’m not familiar with.
Better option is to run a heat pump into that underground loop. You really don’t want underground air getting into your house, and a heat pump will let you cool or warm the air using that same underground loop.
I was thinking of a closed loop system not pumping moldy humid air into a house.
Your idea isn’t bad but does need a space big enough for a technician to service the external unit. Also, the external part of a heat pump isn’t supposed to be enclosed. Not sure if a tunnel counts as enclosed or not.
Ground loop heat pumps are already a thing.
As for maintaining the unit, you just have a service panel you can remove to access it.
Always good to learn something new, thanks.