# Wall and Roof Assemblies need Interstitial Condensation Modelling ### Issue Image: ![[Pasted image 20241219143829.png]] ## Issue Description: - Interstitial condensation occurs when water vapor migrates through building materials and cools to its dew point, condensing within a structure’s layers. - This often happens in poorly ventilated spaces or areas where temperature differentials are significant, such as between heated interiors and cold exteriors. - To mitigate this, it's essential to provide pathways for vapor diffusion that prevent the accumulation of moisture. Strategies include incorporating breathable membranes, ensuring adequate ventilation, and designing assemblies to maintain vapor flow continuity. - The NCC’s Part F6 Condensation Management outlines best practices to address this issue, emphasizing the importance of material selection and system design. - The issue affects both walls and ceilings. ## Actions to Prevent this Issue: - [ ] The Facade Engineer shall model all external roof and wall assemblies and verify that the mould growth index is 0. ## Source