Condensation

The Materials Manager Conduction and CTS > Show Condensation opens Condensation for selected construction. It is used to display condensation data for selected constructions.

For the condensation calculations, the thermal resistance is computed for each layer, enabling interstitial temperatures to be found. Inside and outside conditions are used to compute vapor pressures. The vapor pressure gradient is then computed. The calculation is based on the assumption that condensation occurs at interfaces between material layers. The calculation also computes the amount of water deposited at interfaces during a 60 day winter period. If it is found that condensation occurs within a construction the program recalculates the dew point temperature so that the actual and dew point temperature curves just touch but do not cross. As this touching of lines is often difficult to see graphically, OpenBuildings Station Designer displays the temperature curves before the recalculation to denote condensation risk.

Setting	Description
Graph	When a construction is selected, a condensation calculation is made, and a scaled graph of the construction is displayed, showing the actual temperature distribution and the dew point temperature distribution. If the dew point line touches or crosses the actual temperature line, then condensation will occur. Legend — The two plotted curves are labeled in the legend: Dry bulb and Dew point. When a point is queried by positioning the pointer over one of the curves, the legend becomes highlighted. Similarly the curve is highlighted when it is selected in the legend. Pop up dry bulb and dew point data — To view dry bulb and dew point data, position the pointer over the intersections of the two curves on the condensation graph. A pop up dialog appears displaying the data. Also, when a data point is displayed, perpendicular reference extension lines are drawn on the graph from the point to the temperature and layer axes. Pop up condensation data — To view condensation data, position the pointer over the node (small rectangle) below the condensation graph. A pop up dialog appears displaying the data.
Month	Used to select a month for which to calculate and display condensation data. Condensation in the construction throughout the year is checked. The method involves calculating the condensation or evaporation at each node in the structure for each month of the year and keeping track of accumulated moisture in the construction.
Up	Used to update the condensation data when upward heat flow occurs.
Down	Used to update the condensation data when downward heat flow occurs.
Internal	Used to update the condensation data when heat flow occurs from the inside towards the outside.
Horizontal	Used to update the condensation data when horizontal heat flow occurs.
External	Used to update the condensation data when heat flow occurs from the outside towards the inside.
Internal Dry Bulb	Sets the internal dray bulb temperature.
Internal Saturation	Sets the percentage value for internal saturation.
External Dry Bulb	When checked, you can set the external dray bulb temperature here.
External Wet Bulb	When checked, you can set the external wet bulb temperature here.
Layers	Displays inside and outside dry bulb and dew point temperatures for individual material layers that make up the selected construction definition. Dry bulb in – The inside dry bulb design temperature as defined in the Properties dialog box’s Building Properties. Dry bulb out – The outside dry bulb temperature calculated considering the construction and project weather profile data. Dry bulb loss – The amount of dry bulb energy lost through the material construction. Dewpoint in – The inside wet bulb design temperature as defined in the Properties dialog box’s Properties For: Building data panel. Dewpoint out – The outside wet bulb temperature calculated considering the construction and project weather profile data. Dewpoint loss – The amount of wet bulb energy lost through the material construction.
Condensation table	Condensation in the construction throughout the year is checked. The calculation involves calculating the condensation or evaporation at each node in the construction structure for each month of the year and keeping track of accumulated moisture in the construction. Columns; Condensation – Displays the amount of condensation at the selected Node for each month. Accumulated – Displays the amount of condensation accumulated at the selected Node from previous months for each month. In Structure – Displays the amount of condensation inside the construction for each month. Rows — Displays condensation data for each month. Node selection — Used to select the Node to display condensation data for. Only those nodes which have condensation are listed. The table rows populate when there is condensation where dray bulb and dew point graph line meet.