Wind driven rain and moisture safety of tall timber houses – Evaluation of simulation methods

Abstract: The research work presented here belongs to a transnational project which aims at the development of a moisture risk analysis method used for tall timber facades. The major interest covers heat, air and moisture simulation of wind-driven rain-(WDR) exposed multi-story timber-based building envelopes (over their entire cross-section). While available moisture-safety concepts are often rule based with limited performance-oriented parts and are limited to small-scale housing, further exploration involves exposure of tall facades. State-of-the-art research compiles WDR examinations and available field and laboratory data as well as monitoring and simulation results. That is followed by evaluations of simulation methods at a best practice wall cross-section with the aim of examining the sensitivity and uncertainty of different parameters in relation to outdoor climate. This approach is chosen to discern the complex relations between exposure and vulnerability and the number of different facade detailing. The findings hold a categorization model of facade cross-sections that is used for risk analysis to describe moisture impact and reaction of functional layer groups. Furthermore, all WDR models and measured data show a high level of uncertainty and simulation results are strongly dependent on that input. An additional consideration of deficiencies and WDR penetration into the core layer of the facade shows only vague results of moisture accumulation. Under these circumstances failure modes of structural members are hard to determine. Therefore, this research is ongoing with a focus on more suitable exposure parameters and calibration of simulation methods for tall timber facades.