Future multifunctional thermal protection systems may integrate self-healing, health monitoring, or active cooling capabilities. However, these capabilities likely require the use of designed-in features, or networks of differentiated materials, within a thermal protection system. The thermal response of insulating thermal protection system materials with designed-in features is assessed experimentally to better understand the impact of designed-in features. A radiant heater facility is used to meet three objectives. (1) The effect of designed-in feature shape and position on the thermal response is examined. It was found that increasing the amount of material removed resulted in higher peak bondline temperatures. Increasing the depth of features resulted in lower peak bondline temperature. (2) The facility is characterized to determine the validity of the pseudo-one-dimensional assumption that is initially applied to the analysis. It can be seen from the experimental data, that this assumption is poor and non-adiabatic boundary conditions need to be considered for the walls of the facility. (3) Finally, the experimental data is to be used as a benchmark to validate computational models. This validation was successfully performed using inverse parameter estimation. The inverse parameter estimation process is also used to estimate true material properties, indicating some material property values were as much as up to 15% higher than literature values.