NFRC SHGC |
  
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NFRC SHGC |
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The secondary heat gain coefficient SHGC is computed following the same procedures as the NFRC U-value. With solar power incident on the glazing, the temperature profile is computed and the total transmission of solar energy into the room is calculated. In addition to the directly transmitted radiation sun light is absorbed by the glazing and converted into heat. The fraction of heat entering the room is computed and added to the directly transmitted portion in order to obtain the final SHGC value.
Due to the temperature dependent gas properties, the computational scheme is complex enough. In order to avoid additional difficulties it is assumed that the absorption of solar radiation is evenly distributed across the depth of the panes - this is not a good approximation in the case of absorptive coatings.
Environmental conditions used in the computation of NFRC SHGC values:
Room temperature: 24°
Outside temperature: 32°
Glazing oriented windward, wind speed: 2.75 m/s
Sky temperature: 32°
Sky emissivity: 1.0
Incident solar power: 783 W/m2
Extracting additional information using optical functions
Besides the U-Value you can extract additional values that are obtained during the computation. You can do so using defining appropriate optical functions in the list of 'Optical functions'. Follow the examples below:
The function 'NFRC SHGC (R, simulation, temperature pane 1)' returns the temperature of pane 1 where panes are counted 1, 2, 3, ... from the exterior to the interior.
The function 'NFRC SHGC (R, simulation, temperature pane 2)' returns the temperature of pane 2 and so forth up to pane 5.
The function 'NFRC SHGC (R, simulation, absorbed power pane 1)' returns the absorbed solar power in W/m2 of pane 1. Use similar expressions for panes 2 to 5.