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wall insulation in IDF file

asked 2019-12-02 18:59:54 -0600

updated 2019-12-04 10:36:33 -0600

Following is the wall insulation in IDF file:

!- wall insulation and framing material: R21

  Material,
    wall_consol_layer,       !- Name
    Rough,                   !- Roughness
    0.1397,                  !- Thickness {m}
    0.05966275,              !- Conductivity {W/m-K}
    120.801,                 !- Density {kg/m3}
    1036.25775;              !- Specific Heat {J/kg-K}

But the calculation result is not equal to R21.

(0.1397m) / (0.05966275W/m-K) = 2.34 m2-K/w = R13.

Why?

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Comments

Where did you take this from?

Julien Marrec gravatar imageJulien Marrec ( 2019-12-03 03:00:40 -0600 )edit

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answered 2019-12-03 12:06:54 -0600

The comment seems to indicate that the layer includes both R-21 cavity insulation and wood framing. Since the framing has a lower R-value than the insulation, the effective R-value for the combined layer will be less than R-21.

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Asked: 2019-12-02 18:59:54 -0600

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Last updated: Dec 03