SIST EN ISO 13788:2013 PDF

Overview

EN ISO 13788:2012 (Corrected version 2020-05) - published by CEN/ISO - defines simplified hygrothermal calculation methods for building components and elements. The standard helps determine the internal surface temperature and assess the risk of critical surface humidity, mould growth, and interstitial condensation caused by water vapour diffusion. It also provides a procedure to estimate the drying time for a wetted layer trapped between high vapour resistance layers and the risk of condensation elsewhere during drying.

Key topics

• Surface humidity and mould risk
  • Calculation of the internal surface temperature below which mould or other surface condensation problems are likely, given interior temperature and relative humidity.
• Interstitial condensation due to vapour diffusion
  • Simplified monthly-step methods to assess vapour diffusion condensation risk inside multi-layer building components during heating, cooling and cold-store conditions.
• Drying of wetted layers
  • Estimation of the time required for a wet layer (between two high vapour resistance layers) to dry and whether interstitial condensation will occur elsewhere during drying.
• Input and boundary data
  • Material/product properties, external and internal boundary conditions, and surface resistances required for calculations.
• Limitations and assumptions
  • The methods assume moisture transport by vapour diffusion only and typically use monthly climate data. They do not account for:
    • Variation of material properties with moisture content
    • Capillary suction and liquid moisture flow within materials
    • Air movement from the interior into components (convective transport)
    • Hygroscopic moisture storage in materials
  • Consequently, results are more reliable for lightweight, airtight constructions with low moisture storage capacity.

Practical applications

• Design checks to avoid mould and internal condensation on walls, roofs and floors
• Early-stage compliance assessments for building envelopes and retrofit projects
• Quick screening of interstitial condensation risk before applying more detailed hygrothermal simulation
• Evaluating drying potential of assemblies after construction moisture or accidental wetting

Who should use this standard

• Architects and building envelope designers
• Building physicists and consultants specializing in hygrothermal performance
• Insulation and façade engineers
• Contractors performing design validation or remedial assessments

Related standards

• ISO 6946 - Thermal resistance and transmittance calculation methods
• ISO 9346 - Hygrothermal vocabulary for mass transfer
• ISO 15927-1 - (Referenced for moisture/climate data handling)

Note: Where convective moisture transport, capillary flow or hygroscopic storage are important, use more advanced hygrothermal simulation methods (e.g., transient coupled heat–moisture models). Keywords: hygrothermal, ISO 13788, interstitial condensation, surface humidity, mould growth, vapour diffusion, thermal insulation.