Water Loads in interstices evaluated by Neutron Imaging and effects on Drying Dynamics of Building Assemblies Post-flooding

As part of a wider effort to tackle flooding issues, this study focuses on investigating the amount of water that remains in the interstitial networks of building envelope assemblies after initial drainage of flooding water, to ascertain the significance of this residual water on the post-catastrophe drying measures. We use neutron radiography to visualize and quantify water in assemblies after immersion. Neutron imaging is a radiographic technique that relies on the high neutron scattering cross-section ofprotium, the major component of water. The experiments were performed at the thermal neutron imaging beamline (NEUTRA) at the Paul Scherrer Institute, Villigen, in Switzerland. Over 60 typical Canadian construction material combinations were tested, including spruce timber, thermal insulation (mineral wool, expanded and extruded polystyrene), tar paper, polyethylene sheets, concrete and gypsum board. The samples measured 8x8 cm2 with 1 cm thickness and interstice sizes between materials varied from the apparent contact (denominated as 0 mm) to 2 mm. The assemblies, placed in the beamline, were submerged for 5 to 15 minutes, and the drainage process was imaged over a 20-minute neutron imaging acquisition. The results show that significant amounts of water are retained within interstice networks, which act as preferential pathways for water uptake in assemblies. This retained water adds moisture load within assemblies post-flooding, affecting the drying process and increasing the risk of long-term damage such as mould growth and wood degradation. Given the recurring flood events in recent years and the associated challenges in disaster management, there is an urgent need to better understand how building envelope assemblies behave during such events. These findings will contribute to improving hvgrothermal model accuracy by incorporating such additional water loads, ultimately aiding in the design of more resilient building assemblies.