// Calculate a room's geometry and find its boundary faces
SpatialElementGeometryCalculator calculator = new SpatialElementGeometryCalculator(doc);
SpatialElementGeometryResults results = calculator.CalculateSpatialElementGeometry(room); // compute the room geometry 
Solid roomSolid = results.GetGeometry(); // get the solid representing the room's geometry
foreach (Face face in roomSolid.Faces)
{
    double faceArea = face.Area;
    IList<SpatialElementBoundarySubface> subfaceList = results.GetBoundaryFaceInfo(face); // get the sub-faces for the face of the room
    foreach (SpatialElementBoundarySubface subface in subfaceList)
    {
        if (subfaceList.Count > 1) // there are multiple sub-faces that define the face
        {
            double subfaceArea = subface.GetSubface().Area; // get the area of each sub-face
            // sub-faces exist in situations such as when a room-bounding wall has been
            // horizontally split and the faces of each split wall combine to create the 
            // entire face of the room
        }
    }
}

' Calculate a room's geometry and find its boundary faces
Dim calculator As New SpatialElementGeometryCalculator(doc)
Dim results As SpatialElementGeometryResults = calculator.CalculateSpatialElementGeometry(room)
' compute the room geometry 
Dim roomSolid As Solid = results.GetGeometry()
' get the solid representing the room's geometry
For Each face As Face In roomSolid.Faces
    Dim faceArea As Double = face.Area
    Dim subfaceList As IList(Of SpatialElementBoundarySubface) = results.GetBoundaryFaceInfo(face)
    ' get the sub-faces for the face of the room
    For Each subface As SpatialElementBoundarySubface In subfaceList
        If subfaceList.Count > 1 Then
            ' there are multiple sub-faces that define the face
            ' get the area of each sub-face
            ' sub-faces exist in situations such as when a room-bounding wall has been
            ' horizontally split and the faces of each split wall combine to create the 
            ' entire face of the room
            Dim subfaceArea As Double = subface.GetSubface().Area
        End If
    Next
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