True to enable volume computation. False to disable it. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2014 
Syntax
Remarks
 When this setting is False, rooms and spaces will be treated as simple extrusions of their 2d boundaries. The volume parameter will report "not computed". When this setting is True, the geometry of rooms and spaces will be trimmed when it intersects elements such as ceilings, roofs, and floors. 
 Examples
 Copy  C#
 Copy  C# public void GetRoomDimensions(Document doc, Room room)
{
    String roominfo = "Room dimensions:\n";
    // turn on volume calculations:
    using (Transaction t = new Transaction(doc, "Turn on volume calculation"))
    {
        t.Start();
        AreaVolumeSettings settings = AreaVolumeSettings.GetAreaVolumeSettings(doc);
        settings.ComputeVolumes = true;
        t.Commit();
    }
    roominfo += "Vol: " + room.Volume + "\n";
    roominfo += "Area: " + room.Area + "\n";
    roominfo += "Perimeter: " + room.Perimeter + "\n";
    roominfo += "Unbounded height: " + room.UnboundedHeight + "\n";
    TaskDialog.Show("Revit",roominfo);
} Copy  VB.NET
 Copy  VB.NET Public Sub GetRoomDimensions(doc As Document, room As Room)
    Dim roominfo As [String] = "Room dimensions:" & vbLf
    ' turn on volume calculations:
    Using t As New Transaction(doc, "Turn on volume calculation")
        t.Start()
        Dim settings As AreaVolumeSettings = AreaVolumeSettings.GetAreaVolumeSettings(doc)
        settings.ComputeVolumes = True
        t.Commit()
    End Using
    roominfo += "Vol: " & Convert.ToString(room.Volume) & vbLf
    roominfo += "Area: " & Convert.ToString(room.Area) & vbLf
    roominfo += "Perimeter: " & Convert.ToString(room.Perimeter) & vbLf
    roominfo += "Unbounded height: " & Convert.ToString(room.UnboundedHeight) & vbLf
    TaskDialog.Show("Revit", roominfo)
End Sub