diff --git a/hub/catalog_factories/usage/nrcan_catalog.py b/hub/catalog_factories/usage/nrcan_catalog.py
index 8caf9d10..c485853d 100644
--- a/hub/catalog_factories/usage/nrcan_catalog.py
+++ b/hub/catalog_factories/usage/nrcan_catalog.py
@@ -130,11 +130,11 @@ class NrcanCatalog(Catalog):
       # ACH
       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)
+      ventilation_rate = space_type['ventilation_per_area'] * cte.CUBICFEET_TO_CUBIC_METERS_HOUR
       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.CUBICFEET_TO_CUBIC_METERS_HOUR\
+                           * occupancy_density
 
       lighting_radiative_fraction = space_type['lighting_fraction_radiant']
       lighting_convective_fraction = 0
diff --git a/hub/helpers/constants.py b/hub/helpers/constants.py
index b147e26d..aba8310c 100644
--- a/hub/helpers/constants.py
+++ b/hub/helpers/constants.py
@@ -23,6 +23,7 @@ METERS_TO_FEET = 3.28084
 BTU_H_TO_WATTS = 0.29307107
 KILO_WATTS_HOUR_TO_JULES = 3600000
 GALLONS_TO_QUBIC_METERS = 0.0037854117954011185
+CUBICFEET_TO_CUBIC_METERS_HOUR=1.699
 
 # time
 SECOND = 'second'
diff --git a/hub/imports/usage/nrcan_usage_parameters.py b/hub/imports/usage/nrcan_usage_parameters.py
index 77afb9d0..df41a06a 100644
--- a/hub/imports/usage/nrcan_usage_parameters.py
+++ b/hub/imports/usage/nrcan_usage_parameters.py
@@ -83,7 +83,7 @@ class NrcanUsageParameters:
     if archetype.mechanical_air_change > 0:
       usage.mechanical_air_change = archetype.mechanical_air_change
     elif archetype.ventilation_rate > 0:
-      usage.mechanical_air_change = archetype.ventilation_rate / volume_per_area * cte.HOUR_TO_SECONDS
+      usage.mechanical_air_change = archetype.ventilation_rate / volume_per_area
     else:
       usage.mechanical_air_change = 0
     _occupancy = Occupancy()