IsoDim Help Internal condensation module


This module is used for finding the needed insulation thickness to avoid condensation inside ducts.

Duct type

Calculations on circular and rectangular ducts can be performed.


When calculating the external heat transfer coefficient the orientation of the duct is needed.


Use the outside dimension of the duct (without insulation).


Three parameters are needed:
  1. The air temperature inside the duct.
  2. The airflow rate in the duct
  3. The relative humidity of the air inside the duct

Facing (outside surface)

This section sets the emissivity of the outside surface of the duct. The droplist contains typical values for different materials.


Description of the conditions around and inside the duct. Ambient (surrounding) temperature is used in all calculations. For outdoor conditions the wind speed also has to be given. In this module the conditions should be set for 'worst case' (i.e. the conditions most likely to cause external condensation).

Uninsulated suspensions

This is a simplified way of including the extra heat loss due to the duct suspensions. For outdoor installations 25 % heat loss is added, for indoor installations 15 % is added.


Select an insulation product from the droplist the necessary thickess will be calculated.

Calculated results

Results are shown in one table, two sets of values are shown, one for the needed calculation thickness to avoid condensation and one for the closest standard thickness for the chosen insulation product.