Energetic materials with granular microstructures find wide applications in military and civilian sectors. A comprehensive understanding of their shock response is crucial for the development of safer explosives and predictive models. Initiation of the explosive reaction, a critical safety concern, is believed to be triggered by the formation of hotspots, i.e., localized high-temperature regions. Although direct observation of hotspots remains elusive, computational simulations offer a window into their behavior. This work investigates effect of porosity on reactivity of hotspots in Pentaerythritol Tetranitrate (PETN) and potential shock surrogate Meso-Erythritol (ME). Building upon findings that link hotspot size and temperature to material heterogeneity, this research integrates experimental characterization of ME and mesoscale simulations of both ME and PETN to quantify how the pore distribution influences hotspots. Results showed that shock impedance of ME is within 10% of PETN up to 1 GPa, highlighting its potential as a shock surrogate for weak shocks. Gas gun tests with ME validated Hugoniot parameters in literature, which were used in a P-α compaction model, validating that mesoscale simulations of shock loaded ME agree with experiments within measured uncertainty. This mesoscale approach was then applied to PETN by using synthetically generated microstructures, which demonstrates that enlarging pore size in PETN results in more individually reactive hotspots and greater variability in thermodynamic states over time than increasing pore count or starting with a lower porosity. A higher pore count produces a more right-skewed temperature distribution, indicating a greater total number of hotspots compared to other conditions. Simulations also show that air in individual pores lowers the peak hotspot temperatures due to work done compressing the air and affects secondary hotspot formation. Hotspots within 0.15 μm can react at temperatures below 800 K, their proximity enabling them to bypass thermal quenching via local heat transfer.