My first floor has a bump out over the walk out basement. There is a vinyl soffit built around the joists where they extend out over the house foundation. There is insulation in the bay's between the joists but no framing that prevents air from coming in between the joists bays and going under the first floor ( i.e., looking in from the outside, if I remove the insulation, I can look all the way down the joist bays into the space between the basement ceiling and first floor subfloor. Shouldn't there be some type of blocking between the joists at the foundation that prevents outside air from coming into this space, or is insulation all that is needed? The floor above this does get cold in the winter, and on really cold days the kitchen pipes freeze. Is it standard building practice just to use insulation in this space, or do I need to add some other barrier to air flow?