Glazing Assemblies

By default EnergyPlus models glazing and frames separately through separate window and frame objects. This topic discusses some of the issues related to modelling overall glazing assemblies including the glazed window and opaque frame elements.

There are two general ways to model glazing assemblies in DesignBuilder:

• Data for glass and frame are entered separately where "glass only" properties are defined in the glazing component selected and frame data is defined on the Openings tab under Frame and Dividers. Note that when using this method EnergyPlus is not able to calculate an overall assembly U-value from separate window and frame data. If this output is required is can be done either approximately by adding the parallel conductance of the window and frame and taking the reciprocal or in more detail in a tool such as WINDOW.

• Data for whole glazing assembly is entered directly. This is done using the 2-Simple glazing definition method and entering whole assembly U-value, solar and light transmission data in the glazing component selected on the Openings tab. In this case, to avoid double-counting the impact of the frame, it is important to remove the frame on the Openings tab for all windows using the whole assembly glazing system by unchecking the Has frame/dividers checkbox. If you only have access to "glass only" solar and visible transmission data then these can be multiplied by 1 minus the frame fraction to calculate the whole assembly solar and visible transmission values.

See the Dimensions (Walls) topic for details on how glazing dimensions are written to EnergyPlus IDF.