Indoor relative humidity and window condensation risk in a dwelling with built-in moisture in AAC masonry: a simulation case study

With the spread of wooden frame houses, masonry buildings are disadvantaged by longer construction times due to necessary technological breaks. One such break is drying built-in moisture. Autoclaved aerated concrete absorbs considerable moisture because of its porous structure, whether from heavy rain or other construction incidents. Previous laboratory experiments demonstrated the difficulty of drying masonry after the early application of external polystyrene insulation. These findings motivated the authors to extend the analysis to whole-building simulations under different occupancy scenarios. Using an advanced simulation tool WUFI Plus, this study quantified the impact of wet masonry made of autoclaved aerated concrete insulated from outside with polystyrene foam on the indoor relative humidity increases. After 3 months of occupancy, indoor relative humidity in the wet-masonry cases was still 15–26% points higher than in the corresponding dry-masonry cases, depending on the occupancy scenario. The practical impact of higher indoor relative humidity on potential window condensation at the beginning of occupancy was evaluated. Under the Standard occupancy scenario, the number of hours during which the glazing surface temperature remained below the dew-point temperature increased from 434 h in the dry-masonry case to 1,110 h in the wet-masonry case.