Hygrothermal performance of historic massive wall: when is 2D simulation necessary?

Syracuse, NY

Hygrothermal analysis of historical building envelopes is crucial in ensuring their durability and enhancing their performances. The use of hygrothermal dynamic simulation is the most effective approach to predict moisture related damages or risk of mould growth on ancient masonry envelopes. However, simulating the hygrothermal behaviour of a historic wall composed by stones or bricks and mortar joints, with a detailed two-dimensional (2D) model, is typically a complex and time-consuming process. For this reason, in numerical models, composite walls are often simplified with a one-dimensional (1D) layer, neglecting the mortar joints. An oversimplified numerical model could affect the evaluation of a retrofit intervention and lead to inadequate design choices. This study evaluates when the description of a historic wall as a 1D homogenous layer leads to an acceptable level of accuracy and when it is necessary the use of a more precise 2D model. We quantified the error by comparing 1D and 2D simulations of different massive walls in three Italian climate conditions. We examined a possible retrofit intervention with different internal insulation systems considering vapor tight, vapor retardant and capillary active solutions. Although simplified 1D models are reliable for thermal parameters, we have identified a different behavior regarding the hygric parameters. Whereas for a capillary active insulation system the 1D and 2D simulations show a reasonable agreement, the 1D approximation is no longer acceptable in the case of vapour closed insulation systems as it leads to large deviations. Knowing when it is possible to implement a simplified 1D model and quantifying the introduced error will support architects and energy consultants in the design process. It will guide them in the choice of the most suitable model depending on their specific requirements.

https://surface.syr.edu/ibpc/2018/posters/20