A glass fracture routine has been successfully implemented in the BRANZFIRE zone model, based largely on the heat transfer model developed by Sincaglia and Barnett and the fracture criterion of Pagni and Joshi. A second implementation of the model has been successfully created as a spreadsheet. The BRANZFIRE implementation has been compared against an existing glass fracture model, BREAK1 and against a series of experiments. The BRANZFIRE glass fracture model has been found to consistently predict marginally later fracture times than BREAK1 over a range of simulations. BRANZFIRE’s fracture time prediction compared well with the experimental results. A Monte Carlo based sensitivity analysis found that fracture strength was the most important input variable, though this is largely attributable to the large standard deviation of the probability distribution used for this input.