I have a split level where the family room is 5 steps down from the main floor. The room has full windows and the bottom 3 feet or so of the room is below ground while the rest is above ground. I recently removed some drywall and found there was no insulation behind it. Once I pulled off the drywall there were just studs attached to the foundation wall. Should there be insulation in there or is there some moisture issues with below ground walls that require them to remain free of insulation? Is regular fiberglass insulation suitable or would insulation boards be better?