I have a 1919 house on a raised foundation. Dirt under the house. There is no wall under the house separating the underside of the porch area to the underside of the main living area. Porch is covered. Should I build a wall separating the areas or should I insulate the bays between the joists? If I were to build a wall, should I just lay pressure treated wood (ground contact rated) on the dirt and just build to the joist and then insulate that wall? I live in California and the temp during the winter gets down around 25-30 and the summer it gets up around 100+. The wall area above the wall separating the main living area from the porch was also open to the ceiling / roof area over the porch with no insulation. It was separated from the main area by 1/8 to 1/4 thick wood planks and then a 1/8 thick paperboard which was textured and painted. All ready plan to put up insulation between these areas. Should I put plywood on the porch side to separate those areas too, or just run the insulation up to the ceiling and dry wall over it on the living area side?