My place will have a 1600 sf basement with ICF walls. (Westcliffe Colorado). It will be built into a slope. The north side which will have two Pella Low E argon windows will be completely out of the ground. The south end and part of the east and west will be below ground level. The west side will have one Pella window There will be a 12' garage door on the east (R12 to R18) and a steel walk in door. Any ideas on whether it will ever get to below freezing in the basement if I am not there all winter? If so I need to plan on winterizing or install some kind of heat source that I can leave on year round at 40-45 degrees. Also any ideas on whether the basement would not heat or cooling? I was planning on a small mini split for the bedroom and bath down there. Thanks

With the 12' garage door you would be best to allow some heating into the basement, probably best to go with an electric space heater. With no passive solar heat from south facing windows and the leakiness of the garage door and low R value of the windows expect it to get cold in the winter. However, in the summer you will probably get away with not having to cool the space down since your openings will be in the shade and half of it is submerged.