diff --git a/city_model_structure/attributes/internal_gains.py b/city_model_structure/attributes/internal_gains.py
index 1cf6ecd1..0d509cf1 100644
--- a/city_model_structure/attributes/internal_gains.py
+++ b/city_model_structure/attributes/internal_gains.py
@@ -7,8 +7,9 @@ Copyright © 2020 Project Author Guille Gutierrez guillermo.gutierrezmorote@conc
 
 class InternalGains:
   """
-  InternalGains class
-  """
+    InternalGains class
+    """
+
   def __init__(self):
     self._average_internal_gain = None
     self._convective_fraction = None
diff --git a/city_model_structure/attributes/surface.py b/city_model_structure/attributes/surface.py
index 65be7837..b364553a 100644
--- a/city_model_structure/attributes/surface.py
+++ b/city_model_structure/attributes/surface.py
@@ -70,7 +70,6 @@ class Surface:
     """
     Set surface short wave reflectance
     :param value: float
-    :return: None
     """
     self._swr = value
 
diff --git a/city_model_structure/city_object.py b/city_model_structure/city_object.py
index 10d5181e..6e3c7a11 100644
--- a/city_model_structure/city_object.py
+++ b/city_model_structure/city_object.py
@@ -105,6 +105,17 @@ class CityObject:
         return s
     return None
 
+  def surface_by_id(self, identification_number) -> Union[Surface, None]:
+    """
+    Get the city object surface with a given name
+    :param identification_number: str
+    :return: None or Surface
+    """
+    for s in self.surfaces:
+      if str(s.id) == str(identification_number):
+        return s
+    return None
+
   @property
   def centroid(self):
     """
diff --git a/city_model_structure/monthly_to_hourly_demand.py b/city_model_structure/monthly_to_hourly_demand.py
index 6f2412c8..6b8f2e01 100644
--- a/city_model_structure/monthly_to_hourly_demand.py
+++ b/city_model_structure/monthly_to_hourly_demand.py
@@ -18,10 +18,10 @@ class MonthlyToHourlyDemand:
     self._building = building
     self._conditioning_seasons = conditioning_seasons
 
-  @property
-  def hourly_heating(self):
+  def hourly_heating(self, key):
     """
     hourly distribution of the monthly heating of a building
+    :param key: string
     :return: [hourly_heating]
     """
     # todo: this method and the insel model have to be reviewed for more than one thermal zone
@@ -43,13 +43,13 @@ class MonthlyToHourlyDemand:
         for day in range(1, month_range[1]+1):
           external_temp_med = 0
           for hour in range(0, 24):
-            external_temp_med += external_temp['inseldb'][i]/24
+            external_temp_med += external_temp[key][i]/24
           for hour in range(0, 24):
             if external_temp_med < temp_set and heating_schedule[month-1] == 1:
               if occupancy[hour] > 0:
-                temp_grad_day.append(temp_set - external_temp['inseldb'][i])
+                temp_grad_day.append(temp_set - external_temp[key][i])
               else:
-                temp_grad_day.append(temp_back - external_temp['inseldb'][i])
+                temp_grad_day.append(temp_back - external_temp[key][i])
             else:
               temp_grad_day.append(0)
 
diff --git a/imports/usage_feeders/ca_usage_parameters.py b/imports/usage_feeders/ca_usage_parameters.py
index 2cb3b6dd..592c2f5d 100644
--- a/imports/usage_feeders/ca_usage_parameters.py
+++ b/imports/usage_feeders/ca_usage_parameters.py
@@ -7,7 +7,7 @@ import sys
 
 from imports.usage_feeders.hft_usage_interface import HftUsageInterface
 from city_model_structure.attributes.usage_zone import UsageZone
-
+from city_model_structure.attributes.internal_gains import InternalGains
 
 class CaUsageParameters(HftUsageInterface):
   """
@@ -48,7 +48,17 @@ class CaUsageParameters(HftUsageInterface):
   @staticmethod
   def _assign_values(usage_zone, archetype):
     usage_zone.usage = archetype.usage
-    usage_zone.internal_gains = archetype.internal_gains
+    # gue to the low 'tipado' of python, usage_zone.internal_gains = archetype.internal_gains assigns the wrong
+    # object type to usage_zone.internal_gains. Therefore, this walk around has been done.
+    internal_gains = []
+    for ig in archetype.internal_gains:
+      internal_gain = InternalGains()
+      internal_gain.average_internal_gain = ig.average_internal_gain
+      internal_gain.convective_fraction = ig.convective_fraction
+      internal_gain.radiative_fraction = ig.radiative_fraction
+      internal_gain.latent_fraction = ig.latent_fraction
+      internal_gains.append(internal_gain)
+    usage_zone.internal_gains = internal_gains
     usage_zone.heating_setpoint = archetype.heating_setpoint
     usage_zone.heating_setback = archetype.heating_setback
     usage_zone.cooling_setpoint = archetype.cooling_setpoint