Freeze-thaw risk in solid masonry : are moisture reference years able to represent real climate conditions?

Today, there is no consensus on the selection method of representative exterior boundary conditions when performing HAM (Heat Air Moisture) simulations on building envelopes. Many existing methods to select moisture reference years (MRY) fail to provide an acceptable validation in terms of quantified risk assessment. Although new methods have been suggested during the past few years, the influence of several parameters on the selection of “critical years” in long-term datasets still needs to be assessed. The objective of this paper is to validate the application of MRY’s to evaluate freeze-thaw risk in retrofitted solid masonry. Furthermore, the influence of the chosen wall assembly, damage criterion, preconditioning and start date of the evaluation period on the ranking of critical years is assessed, using a 31-year meteorological dataset of Brussels. Results indicate that for a given wall assembly and freeze-thaw criterion, as well as a smart start date of the evaluated period, single year simulations entail a similar ranking of critical years as the corresponding year in the 31-year simulation. The number of critical freeze-thaw cycles only varies between 0 - 2 cycles (0 - 2.9%). However, changing the wall assembly and damage criterion, alters the top 5 ranking of critical years substantially.