Techniques for designing and fabricating thermal support regions via additive fabrication are described. Defects produced as a result of temperature differentials within an additive fabrication device that forms parts by sintering particles of material may be mitigated or avoided by directing energy to regions around a part that is sufficient to heat the material and cause it to partially sinter, but not enough to fully sinter the material. The mechanical properties of such a thermal support region may resist the effects caused by temperature gradients. In addition, or alternatively, the heating of the thermal support region material may reduce heat lost by nearby sintered material. In either or both cases, the thermal support region acts as a kind of 'volumetric armor' that surrounds some or all of the part and protects the part from defects.