It is recognized that moisture can damage the structure and internal environment of buildings. British and European Standards support the relevant legislation, regulations and statutory guidance in this field (such as Approved Documents in England and Wales). They are sometimes directly referenced in certification processes and in guidance documents.
Until recently, most standards for buildings have been primarily concerned with the design and construction of new buildings. Less attention has been paid to the increasingly important fields of retrofit and the renovation of existing buildings, especially older, solid-wall buildings, where issues of moisture movement and risk are of a different nature from those found in new cavity construction.
Historically, types of moisture have been divided into discrete categories such as driven rain, flooding and condensation. In reality, however, these types often overlap and interact.
There are also new challenges arising from the changing ways in which buildings are being constructed, retrofitted and lived in, particularly regarding attempts to create low-energy buildings with increasing amounts of insulation and airtightness.
Problems can also arise from lack of data and research on moisture issues in buildings, and the inherent complexity of interactions between climate, building fabric, services and occupant behaviour.
This paper has been prepared by the Sustainable Traditional Building Alliance (STBA), with the support of the former Department of Energy and Climate Change (now the Department for Business, Energy and Industrial Strategy) and is published by the British Standards Institution (BSI). It offers a new framework for the development of future moisture standards, and guidance and practice that addresses the challenges of moisture risk. It suggests an integrated and safe approach to moisture risks in buildings for the future. It has been created to stimulate and assist discussion in revising existing standards and guidance such as BS 5250:2011, Code of practice for control of condensation in buildings.
It should be reiterated that this paper is only a framework for the future development of standards and guidance, and not a standard or guidance per se. As such, it is not endorsed by BSI and should not displace any existing standards. The framework suggested needs testing, both theoretically and in practice, so that workable and successful formal standards and construction processes can evolve.
The general approach of this paper has been endorsed by academic experts and mainstream practitioners and is backed by considerable research both in the UK and in Europe. As such, it stands as a clear statement of current understanding of moisture risk in buildings: the science, causes and practical approach which should be taken to manage the risk.
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