Insulating outside the crawlspace – GreenBuildingAdvisor

It’s much more difficult to retrofit insulation on the exterior of a foundation wall since you have to excavate alongside that wall, which will damage any landscaping that may be present, and also risks damaging the foundation itself. It is much easier, and safer for the structure, to add insulation on the interior where none of these risks exist.

If you are doing new construction, then insulating on the exterior of the foundation is an option (although some still prefer to insulate the interior), but for retrofits, interior insulation is far easier to install and there isn’t enough of a performance difference to justify all the additional effort, cost, and risk involved in trying to insulate on the exterior instead.

Bill