Walls. Basement walls should be insulated with non-water sensitive insulation that prevents interior air from contacting cold basement surfaces—the concrete structural elements and the rim joist framing. … The best insulations to use are foam based and should allow the foundation wall assembly to dry inwards.

Is it OK to not insulate basement walls?

Impervious insulation is always an excellent idea for basement walls, but it’s absolutely essential where the floor joists of the level above meets outside walls along the edges of a basement ceiling.

Is it necessary to insulate basement walls below grade?

Your best bang for the dollar in this instance is to insulate the coldest part of the wall, again typically to 2-feet below grade. … The reason why you’d want to insulate the whole wall is not so much because of the energy savings, but because a stone wall, and dirt or crushed rock floors let in a lot of moisture.