Condensation risk analysis: A practical approach

Abstract

The UK’s commitment to achieving net zero by 2050 stresses the necessity for highly energy-efficient building structures, emphasising a fabric-first approach. Inadequate design or execution can lead to unintended consequences, particularly condensation within the building envelope, posing risks of structural damage and mould growth. This paper delves into the intersection of precise design and a sustainable future, highlighting the crucial role of condensation risk analysis (CRA). CRA is vital for assessing moisture activity, predicting condensation and implementing measures to avoid or minimise associated risks. The study evaluates various moisture sources and mitigation strategies, focusing on rain ingress, construction moisture, rising damp, internal and external vapour pressure and moisture-laden warm internal air. Comparing two widely used CRA methods, the dewpoint method and hygrothermal numerical simulation (HNS), the paper emphasises their strengths and applications. Practical guidance on selecting the right CRA method based on project-specific scenarios, fabric types and moisture risks is provided. Case studies demonstrate the application of both methods in a conventional timber frame with a brick façade and internal wall insulation on solid brick masonry. Legal and regulatory considerations, including BS 5250:2021, are discussed, highlighting the importance of adherence to standards in effectively managing moisture-related challenges. The paper concludes by emphasising the significance of CRA in ensuring the longevity and efficiency of building envelopes, serving as a valuable resource for building surveying professionals.