Comparison of different frost models with hygrothermal simulations to better understand frost damage in porous building materials

Frost damage is one of the most important degradation phenomena of brick facades. Evaluating the risk of frost damage in advance is of utmost importance considering the difficulty of repairing frost damage without replacing the materials, which may not be an option for protected heritage facades. Various performance criteria and methods have been developed over the past decades to assess the risk of frost damage. However, these methods are derived from frost tests under extreme conditions, such as high saturation levels and very low freezing temperatures, and do not represent realistic conditions for mild climates. In 2019, Feng et al. tested four different bricks under milder conditions to understand the relationship of frost damage with freezing temperature and saturation degree. The research in this paper combines the results of Feng's study with hygrothermal simulations, which prove to be a valuable tool for assessing the risk of deterioration of facades of masonry buildings. In this paper, the frost decay assessment methods like the Fc-index, GC-factor and counting the critical freeze-thaw cycles are examined, discussed and finally dismissed. Finally, a more representative frost decay risk assessment method is proposed. •Assess frost risk with response-based methods, not material sensitivity methods.•Hygrothermal simulations provide relevant insights on frost damage understanding.•Various frost assessment methods yield diverse climate response outcomes.•More freeze-thaw cycles do not necessarily result in higher frost damage.•Offering a time-resource dependent framework for accurate frost damage assessment.