There’s a lot going on mechanically with this home. To get a better idea of space requirements, here is a concept showing what will to fit into this 20‘x20’ space. Here’s a short list:
ERV
Water source heat pump
HVAC mechanical panels
Fire sprinkler system
Refrigerator/Freezer
Washup sink
Tools and work bench
Battery rack and inverter for solar, hydro and someday, wind.
Busse micro sewage treatment
Rope ladder to upstairs