Unavoidable thermal bridge on foundation, exterior vs interior insulation – or a mix of both? – GreenBuildingAdvisor

Hi everyone,

I am in the situation of having a poured concrete retaining wall connected to the foundation, causing an unavoidable thermal bridge through the concrete into the conditioned space.  The design intent was to insulate the exterior of the foundation for all the known beneficial reasons, but this unavoidable thermal bridge has me questioning –  is it better to do 100% interior insulation, or have a mix of exterior and interior insulation, with an overlap on the interior of 10′ to achive an approximate r10 w/ thermal bridge?

In a similar Q&A, Holladay says “Even better would be to put 100% of your basement insulation on the interior, or 100% of your basement insulation on the exterior.”  

Exterior and interior foundation insulation crossover

Is this really true from a thermal perspective, or is this a more practical answer given the additional materials and labor?

Thanks!