Preventing Damage by Updating Moisture Control Standards

Despite progress in moisture control analysis, repairing moisture damage is still a considerable cost factor in the building sector. While there are many reasons for the lack of improvement during the last decades, inadequate moisture control standards are certainly also to blame. In many countries, interstitial condensation calculations according to Glaser are the sole means for assessing moisture control design, neglecting other important moisture loads such as driving rain, construction moisture and air infiltration. To overcome this lopsided focus on vapour diffusion, the update of the German moisture control standard has restricted the applicability of the Glaser method and introduced a normative Annex on performance evaluation by hygrothermal simulation. Recently, a new project has started to develop advanced models helping to evaluate the simulation results. Currently, it is already possible to assess the risk of mould growth, rot, and critical moisture accumulation by methods referred to in this standards. Also addressed in the standard is the selection of critical indoor and outdoor boundary conditions. Thus, it is officially encouraged to perform hygrothermal simulation, giving architects and engineers the chance to design more moisture tolerant and ultimately more durable constructions. Considering the necessity to reduce the carbon footprint of buildings, the application of hygrothermal simulation provides the opportunity to use more innovative renewable and recycled materials that could not adequately be judged by the Glaser method. Another benefit presents the analysis of construction resilience in case of natural disaster such as flooding or extreme rain events.