Drainage Balance Testing of Mineral Wool Insulation

Modern building enclosure designs often make use of rainscreen cladding and a layer of continuous insulation installed outboard of a drainage plane/water control layer. Although mineral wool insulation has been used successfully in rainscreen and masonry cavity walls for several decades, the relative unfamiliarity of the North American building industry with the product has generated questions regarding the moisture-related performance of mineral wool. This report documents testing conducted by RDH-BSL to determine if ROXUL CavityRock DD (the most common ROXUL product used in drained wall systems) would absorb water during rain events and if the insulation performance would be affected.

Water was sprayed over the exterior cladding surface of wall assemblies using both CavityRock and XPS as the continuous insulation on the exterior of a water barrier. Various configurations were tested and their performance compared by measuring both the change in weight of the wall assembly (water stored), and the volume of water that drained off different surfaces within the assembly (water drained). After the water spray was stopped, the residual amount of water in the assembly and its drying rate were measured.

Note: This report was prepared for ROXUL Inc. and is published with permission