Condensation Prediction with IESVE Software

By Liam Buckley on Tuesday 27 March 2018

Did you know  there are up to three different approaches you can take to predicting condensation in a building design, using IESVE software? In this DiscoverIES post, we highlight these three methods.

Condensation will occur and form on a surface, when the temperature of the surface is below or equal to the dew point temperature of the air surrounding the surface.

1. Interstitial condensation within opaque construction assemblies
A regression analysis of the weather data in the VistaPro application will tell us when a typical design day for humid conditions might occur. In the Apache application, those condistions can be plotted against the dry bulb temperature, vapor pressure and saturated vapor pressure within any construction material.

Should the vapor pressure be equal or greater than the  saturated vapor pressure, interstitial condensation will occur. In such case, a vapor barrier is recommended, or adjustments of the internal Relative Humidity setpoints.

2. Surface condensation on internal building surfaces (e.g. Glazing)

Before performing an annual sub-hourly simulation, it is important to include all analyses that might impact building surface temperatures.

When analyzing results, a common visual aid is a heat map (color gradient). In the example below, hours in red indicate condensation occuring on a window for one hour.

Left to right is January to February. Top to bottom is hours 00:00 – 23:59.

3. Surface condensation on mechanical equipment (e.g. Chilled beams)

The risk of condensation occuring on a chilled beam can be analyzed with the ApacheHVAC application. In this example, the secondary chilled water loop has a higher chilled water flow & return temperature, when compared to the primary chilled water loop. The risk is that this higher chilled water (piping or beam) could be lower than the dew point temperature at the beam. This example and example 2 can be analyzed with the Custom Variables in VistaPro.

Secondary chilled water loop, serving chilled beams, with high chilled water flow & return temperatures.

Click here to find out more about the IESVE Applications used in these three methods.