Condensation Analysis

Condensation analysis tab on Constructions Dialog.


DesignBuilder Condensation Analysis allows you to generate reports on the occurrence of interstitial and surface condensation based on the ISO 13788 standard.


The analysis is accessed from the Condensation analysis tab on the Constructions dialog. Controls are provided under the Options header to control the outputs generated and there are also tools to allow you to set internal and external boundary conditions for the condensation calculations.


The moisture vapour resistance properties for each material used in the construction layers must be entered on the materials dialog for accurate condensation analysis results.


Data under the Options header allows you to set various calculation and display options for the condensation analysis.

Show Glaser diagram

Check this option if you would like to view a Glaser diagram showing a graphical section through the construction with temperature, partial vapour pressure and saturated vapour pressure data plotted.


When viewing a Glaser diagram select the month from the drop list. The default option is 13-Worst case month where DesignBuilder displays results for the month with the worst case of moisture build up.

Show interstitial condensation details

If you would like to view details of the monthly and cumulative condensation build up for each interface with condensation then check this option. In this case, if condensation is present you will see output similar to:



If you requested interstitial condensation details then you should enter the interface number here. The definition of each interface with condensation is given under the Condensation Interfaces heading in the report.

Surface condensation calculation

To see surface condensation details check this box. In this case you should enter further details to define the boundary conditions as explained below.

Environment source

Select from:



In all cases monthly external conditions are defined in the Boundary data.

Fixed internal air temperature

Fixed internal RH

Humidity class

Show surface condensation details


Example Output

An example report generated by the Condensation analysis tool is shown below.

Condensation Analysis Report

Interstitial Condensation

Interstitial condensation occurs at one or more interfaces but all condensate is predicted to evaporate during the summer months.

The risk of degradation of building materials and deterioration of thermal performance as a consequence of the calculated maximum amount of moisture shall be considered according to regulatory requirements and other guidance in product standards.

Condensation Interfaces

Number of condensation interfaces: 2

Distance of condensation interface 1 from the external surface: 100mm

Distance of condensation interface 2 from the external surface: 108.333333333333mm

Surface Condensation

Thermal quality Good. Mould growth unlikely.


Boundary Data

The Boundary data dialog can be accessed from the link on the info panel of the Condensation analysis tab.