Recent research suggests that every insulation material undergoes failure in varying degrees of severity. Based on data derived from specified mould risk failure criteria, this study developed a novel equation to quantify the performance of insulation materials/systems following such transient conditions. Transient conditions performance (TCP) was quantified using the period after exceeding the risk criteria, the duration of exceedance and recovery time. The current formulation does not readily distinguish between materials based on their ability to cope with transient conditions. Further research was initiated to incorporate more diverse variables with which to expand the specificity of the TCP quantification.