diff --git a/hub/catalog_factories/usage/nrcan_catalog.py b/hub/catalog_factories/usage/nrcan_catalog.py
index 8caf9d10..337f5868 100644
--- a/hub/catalog_factories/usage/nrcan_catalog.py
+++ b/hub/catalog_factories/usage/nrcan_catalog.py
@@ -105,7 +105,8 @@ class NrcanCatalog(Catalog):
     for space_type in space_types:
       usage_type = space_type['building_type']
       space_type_compliance = space_types_dictionary[usage_type]
-      occupancy_density = space_type_compliance['occupancy_per_area']
+      #todo: check, because I think the value is pax per 1000 sqfoot
+      occupancy_density = space_type_compliance['occupancy_per_area']/1000
       lighting_density = space_type_compliance['lighting_per_area']
       appliances_density = space_type_compliance['electric_equipment_per_area']
       domestic_hot_water_peak_flow = space_type_compliance['service_water_heating_peak_flow_per_area']
@@ -128,14 +129,14 @@ class NrcanCatalog(Catalog):
       domestic_hot_water_load_schedule = self._get_schedules(domestic_hot_water_schedule_name)
 
       # ACH
+      #todo: revise with Pilar, some changes done
       mechanical_air_change = space_type['ventilation_air_changes']
       # cfm/ft2 to m3/m2.s
       ventilation_rate = space_type['ventilation_per_area'] / (cte.METERS_TO_FEET * cte.MINUTES_TO_SECONDS)
-      if ventilation_rate == 0:
+      #if ventilation_rate == 0:
         # cfm/person to m3/m2.s
-        ventilation_rate = space_type['ventilation_per_person'] / (cte.METERS_TO_FEET * cte.MINUTES_TO_SECONDS)\
-                           / occupancy_density
-
+      ventilation_rate += space_type['ventilation_per_person'] / (cte.METERS_TO_FEET * cte.MINUTES_TO_SECONDS)\
+                           * occupancy_density
       lighting_radiative_fraction = space_type['lighting_fraction_radiant']
       lighting_convective_fraction = 0
       if lighting_radiative_fraction is not None:
diff --git a/hub/exports/building_energy/idf.py b/hub/exports/building_energy/idf.py
index df817e78..51815614 100644
--- a/hub/exports/building_energy/idf.py
+++ b/hub/exports/building_energy/idf.py
@@ -38,6 +38,7 @@ class Idf:
   _WINDOW_MATERIAL_SIMPLE = 'WINDOWMATERIAL:SIMPLEGLAZINGSYSTEM'
   _ROUGHNESS = 'MediumRough'
   _INFILTRATION = 'ZONEINFILTRATION:DESIGNFLOWRATE'
+  _VENTILATION = 'ZONEVENTILATION:DESIGNFLOWRATE'
 
   _HOURLY_SCHEDULE = 'SCHEDULE:DAY:HOURLY'
   _COMPACT_SCHEDULE = 'SCHEDULE:COMPACT'
@@ -421,7 +422,21 @@ class Idf:
                            Design_Flow_Rate_Calculation_Method='AirChanges/Hour',
                            Air_Changes_per_Hour=thermal_zone.infiltration_rate_system_off * factorreduct
                            )
-
+  def _add_ventilation(self, thermal_zone, zone_name):
+    # for zone in self._idf.idfobjects["ZONE"]:
+    #  if zone.Name == f'{zone_name}_infiltration':
+    #    return
+    schedule = f'Ventilation schedules {thermal_zone.usage_name}'
+    # if schedule not in self._idf.idfobjects[self._HOURLY_SCHEDULE]:
+    #  return
+    # todo: revise ventilation with Pilar
+    self._idf.newidfobject(self._VENTILATION,
+                          Name=f'{zone_name}_ventilation',
+                           Zone_or_ZoneList_Name=zone_name,
+                           Schedule_Name=schedule,
+                           Design_Flow_Rate_Calculation_Method='Flow/Zone',
+                           Flow_Rate_per_Zone_Floor_Area=thermal_zone.infiltration_rate_system_off
+                         )
   def _add_dhw(self, thermal_zone, zone_name):
     fuel_type = 'Electricity'
     method = 'Watts/Area'