Condensation tool

The Condensation Tool is a new tool developed by Passive House Institute, in the commonly used Excel format *.xlsx.

This tool is based on the International Standard ISO 13788:2012 and provides simplified calculation methods that enable calculation of:

• The hygrothermal performance of building components and building elements;

• Internal surface temperature to avoid critical surface humidity;

• Temperature and vapour pressure inside the component to estimate interstitial condensation.

The moisture transfer theory is complex and requires information that is typically hard to gather; the theory requires highly specific knowledge of hygrothermal calculation.

The most common values available for the building materials are not sufficient for describing the moisture transfer process accurately. The designer needs more data e.g. moisture and capillarity function, moisture content of the material, inclination of the component, short and long-wave radiations, hourly climate data etc., to obtain more precise and complete results.

This method brings more reliable results for lightweight and airtight components that do not contain materials with a large water storage capacity. This method (Glaser Method) and this tool are based on simplified calculations. Users should note that where a component is not verified following this methodology, it could in theory be verified using different and more detailed methods e.g. dynamic calculations according to EN 15026. The method is an assessment rather than an accurate prediction tool.

The ISO 13788:2012 is a monthly calculation and does not take into account:

• The variation of thermal conductivity, heat transport and other moisture content and temperature properties;

• Capillary suction, sorption coefficient, liquid transfer and moisture capacity of materials;

• Three- or two-dimensional moisture transport;

• Air leakages through the various layers of the component;

• External climate conditions as solar radiation, rainfall, wind exposure;

• Air, rising damp, rain or underground infiltrations;

• Gravity;

• Moisture transport other than vapour diffusion.

Condensation Tool is composed by these worksheets:

• Instructions: It contains the general information and the necessary instructions about how to use the tool.

• Climate: there are the options to define the exterior and interior climates to use for the verification.

• Assembly: In this worksheet the designer inserts the structure, materials and hygrothermal data of the component to verify.

Thus, the coondensation tool offers an easy and fast way to verify a very complex and important aspect of building construction. It is a steady state analysis and considers only some aspects of the complex moisture transfer. The target is including more aspects of the physical behaviour of the building component to get a deeper analysis, keeping the user interface easy to understand. Together with PHPP (PHI energy balance software) this tool can cover the whole energy design process for buildings.