Overview
ISO 9346:2007 - Hygrothermal performance of buildings and building materials - Physical quantities for mass transfer - Vocabulary - is an international terminology standard that defines the physical quantities, symbols and units used for mass transfer (vapour and moisture transport) in buildings, building elements, components and materials. This second edition (2007) updates the 1987 version and harmonizes terms used in building hygrothermal science (for example, replacing “moisture” with water vapour in several definitions and aligning the symbol for relative humidity to ϕ).
Key topics
- Standardized vocabulary for mass transfer related to building physics (terms and definitions).
- Physical quantities relevant to hygrothermal analysis (names of quantities without numeric values).
- Corresponding symbols and SI units for each physical quantity to ensure consistent reporting and modelling.
- Subscripts and notation conventions used in hygrothermal equations and documentation.
- Indexes and bibliography to support cross-referencing and further reading.
- Harmonization notes (changes from previous edition, incorporation of Amendment 1).
Practical applications
ISO 9346:2007 provides the linguistic and notation foundation needed to:
- Ensure consistent use of terms and symbols in research papers, technical reports and standards relating to vapour diffusion and moisture transport.
- Improve clarity in simulation models and hygrothermal software by standardizing variable names and units.
- Support laboratory testing and material characterization documentation where mass transfer properties are reported.
- Facilitate cross-discipline communication among architects, building physicists, HVAC engineers and material scientists working on moisture control, condensation risk and durability.
Who should use this standard
- Building physicists and hygrothermal modellers
- Structural and façade engineers concerned with moisture performance
- Materials researchers and manufacturers producing moisture-related data
- Standards developers, testing laboratories, and educators preparing technical material or curricula
- Authors of technical reports, specifications and software that handle mass transfer variables
Related standards
- ISO 7345 - Thermal insulation - Physical quantities and definitions
- ISO 9251 - Thermal insulation - Heat transfer conditions and properties - Vocabulary
- ISO 9288 - Thermal insulation - Heat transfer by radiation - Physical quantities and definitions
Note: ISO 9346:2007 is primarily a vocabulary and notation reference - it does not prescribe test methods or performance limits, but it is essential for consistent terminology and unit usage across hygrothermal design, modelling and documentation.