Dew Point

Dew Point Modelling on Speckel

ISO 13788 focuses on assessing interstitial condensation risks by considering influential factors like temperature gradients, humidity levels, material diffusion resistance, and vapour pressure profiles.

ISO 13788, titled “Hygrothermal performance of building components and building elements – Internal surface temperature to avoid critical surface humidity and interstitial condensation – Calculation methods,” provides guidelines to prevent surface condensation by maintaining internal surface temperatures above the dew point and to assess interstitial condensation risks by evaluating temperature and vapour pressure gradients within building components.

Below is a step-by-step outline of the required inputs for Dew Point simulations, calibrated to align with ISO 13788 standard.

ISO 13788 Limitations

ISO 13788 does not account for several critical physical phenomena, including:

• Variations in material properties with moisture content,

• Capillary suction and liquid moisture transfer within materials,

• Air movement into the component via gaps or air spaces,

• Hygroscopic moisture capacity of materials. Thus, the method applies only when these phenomena can be deemed negligible.

Due to the stated limitations above, we recommend dynamic moisture simulations are undertaken where any risk is identified when undertaking a Dew Point assessment as per ISO 13788.