Moisture performance of interior insulated brick wall segments subjected to wetting and drying – A laboratory investigation

Abstract Hygrothermal challenges are introduced when equipping facades of existing masonry buildings with interior insulation. If not addressed, moisture damages to the building envelope may follow. Many measures for overcoming reduction in drying potential have been proposed and studied. Still, more understanding is needed regarding effects of measures. This paper investigates wetting and drying behavior of masonry wall segments mounted in a large-scale building envelope climate simulator, exposing them to a climatic sequence including driving rain. Equipped with interior insulation and embedded wooden beam ends, most wall segments are applied with a smart vapor barrier. This should allow for inward drying during warm exterior climate, while under cold climate, prevent interstitial condensation. A variety in masonry wetting and drying behavior among segments of same brick type was found to partly obscure effects of other parameters such as insulation thickness, brick type and vapor barrier type. Compared to high IRA (initial rate of absorption) brick segments, moderate IRA brick segments show higher drying rates at beam ends and at the interface between interior masonry surface and insulation. During wetting, results were found to be inconsistent. An increased drying of the interface between interior masonry surface and insulation was found to correlate to decreasing insulation thickness and application of a smart vapor barrier over a traditional polyethylene barrier. A similar but less pronounced trend is also detected at beam ends. A smart vapor barrier seemingly improves the drying potential, but it likely needs to be accompanied by other measures.