The host element ID for the load. 
   Namespace:   Autodesk.Revit.DB.Structure  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2015 
Syntax
Remarks
 If the load is hosted this is the id of the AnalyticalModel element that hosts the load. If the load is not hosted, ElementId.InvalidElementId is returned.