NFRC U-value (winter) |
  
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NFRC U-value (winter) |
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The NFRC center-of-glass U-value is computed following the procedure described in the document "WINDOW 4.0: Documentation of Calculation Procedures" (July 1993). The method is based on physical principles and experimental results concerning heat transfer through a glazing system. In an iterative process the temperature distribution in the glazing is obtained, taking into account temperature dependent gas properties in between the panes. Gas properties are not taken from the document mentioned above but from the standard ISO 15099.
The expressions for temperature dependent gas properties have been implemented in objects of type 'Gas' in the list of materials (starting with version 3.79). These objects allow the definition of gas mixtures and re-compute all required gas properties at any given temperature. Make sure that you use objects of this type as filling gas in your layer stacks.
NFRC U-values in CODE are computed using the following environmental conditions (NFRC 100-2010 Winter) :
Room temperature: 21°
Outside temperature: -18°
Glazing oriented windward, wind speed: 5.5 m/s
Sky temperature: -18°
Sky emissivity: 1.0
Incident solar power: 0 W/m2
Extracting additional information using optical functions
Besides the U-Value you can extract additional values that are obtained during the computation, in particular the obtained pane temperatures. You can do so using defining appropriate optical functions in the list of 'Optical functions'. Follow the examples below:
The function 'NFRC U-value (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 U-value (R, simulation, temperature pane 2)' returns the temperature of pane 2 and so forth up to pane 5.