[EnergyPlus_Support] U-Value Calculation

["tobias.leibing" <tobias.leibing@xxxxxx>]

Hey there,

I have some problems with the U-value calculation of EnergyPlus.  For some reason the by EnergyPlus calculated U-values are not correct.

I only look at the U-values from surface to surface, meaning without taking the inside/outside air film into account since these definitely vary in EnergyPlus.

The actual material specifications come from the DOE2.2 Vol.4 Material Library. 

Material,
    CMU,                     !- Name
    Rough,                   !- Roughness
    0.1016,                  !- Thickness {m}
    0.771,                   !- Conductivity {W/m-K}
    1842,                    !- Density {kg/m3}
    837,                     !- Specific Heat {J/kg-K}
    0.9,                     !- Thermal Absorptance
    0.7,                     !- Solar Absorptance
    0.7;                     !- Visible Absorptance

Material,
    Gypsum,                  !- Name
    Rough,                   !- Roughness
    0.15875,                 !- Thickness {m}
    0.16,                    !- Conductivity {W/m-K}
    801,                     !- Density {kg/m3}
    837,                     !- Specific Heat {J/kg-K}
    0.9,                     !- Thermal Absorptance
    0.7,                     !- Solar Absorptance
    0.7;                     !- Visible Absorptance

Material,
    Brick,                   !- Name
    Rough,                   !- Roughness
    0.1016,                  !- Thickness {m}
    1.33,                    !- Conductivity {W/m-K}
    2083,                    !- Density {kg/m3}
    921,                     !- Specific Heat {J/kg-K}
    0.9,                     !- Thermal Absorptance
    0.7,                     !- Solar Absorptance
    0.7;                     !- Visible Absorptance


Material:AirGap,
    Air Space,               !- Name
    0.16;                    !- Thermal Resistance {m2-K/W}



Construction,
    EXTWALL80,               !- Name
    Brick,                   !- Outside Layer
    CMU,                     !- Layer 2
    Air Space,               !- Layer 3
    Gypsum;                  !- Layer 4



The manually calculated U-value for my construction is 2.16 W/m2K; EnergyPlus calculates a value of 0.74 W/m2K...

I think I've double-checked now everything at least three times but still couldn't resolve that issue.

It does neither work in my current project file nor in one of the example files.

I have uploaded the idf-file in the file section; name: "U-Value Calculation"


Thank you,
Tobias




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