diff --git a/hub/city_model_structure/building_demand/thermal_zone.py b/hub/city_model_structure/building_demand/thermal_zone.py
index f4262aec..02924ea9 100644
--- a/hub/city_model_structure/building_demand/thermal_zone.py
+++ b/hub/city_model_structure/building_demand/thermal_zone.py
@@ -62,6 +62,10 @@ class ThermalZone:
     self._domestic_hot_water = None
     self._usage_name = None
     self._usages = usages
+    self._usage_from_parent = False
+    if usages is None:
+      self._usage_from_parent = True
+     
 
   @property
   def parent_internal_zone(self) -> InternalZone:
@@ -74,11 +78,10 @@ class ThermalZone:
   @property
   def usages(self):
     """
-    Get the thermal zone usages including percentage with the format [percentage]-usage_[percentage]-usage...
-    Eg: 70-office_30-residential
+    Get the thermal zone usages
     :return: str
     """
-    if self._usages is not None:
+    if self._usage_from_parent:
       self._usages = copy.deepcopy(self._parent_internal_zone.usages)
     return self._usages