If only basic manufacturers data on the glazing system is available then you may need to use the more approximate Simple glazing definition method. In this case the glazing properties for the overall glazing system are defined using the three parameters:
You can read details of the method used behind the scenes in EnergyPlus to represent the simple glazing definitions in the report Modeling Windows in Energy Plus with Simple Performance Indices by Dariush Arasteh, Christian Kohler and Brent Griffith.
This field describes the value for window system U-Factor, or overall heat transfer coefficient. Units are in W/m2K. This is the rated (NFRC) value for U-factor under winter heating conditions. The U-factor is assumed to be for vertically mounted products.
Note: The maximum U-value is 5.8 W/m2K because this is the most conductive glazing system possible given the above standard conditions that can realistically be achieved. If you need to model a glazing system with a very high U-value (above 5.8 W/m2K) the published rating probably contains the frame, in which case you should add a frame to obtain the required overall glazing + frame U-value.
Enter the value for solar heat gain coefficient for the combined glazing system, a fractional value from 0 to 1 without units. This is the rated (NFRC) value for SHGC under summer cooling conditions and represents SHGC for normal incidence and vertical orientation.
g-values and SHGC values ranges from 0 to 1, a lower value representing less solar gain. Shading coefficient values are calculated using the sum of the primary solar transmittance (T-value) and the secondary transmittance. Primary transmittance is the fraction of solar radiation that directly enters a building through a window compared to the total solar insolation, the amount of radiation that the window receives. The secondary transmittance is the fraction of inwardly flowing solar energy absorbed in the window again compared to the total solar insolation.
Enter the visible transmittance for the glazing coefficient, a fractional value from 0 to 1. It is the rated (NFRC) value for visible transmittance at normal incidence.
Simple glazing data can either include or exclude the effect of the frame. If the glazing data includes the frame then you should make sure to switch off frames in the openings model data to ensure that they are not double-counted.
Note: When using the simple glazing definition it is important to understand that there may be significant differences in performance between the simple window system and the usual more detailed model. This option should therefore only be used when layered data is not available.