diff --git a/recommendations/optimiser/optimiser_functions.py b/recommendations/optimiser/optimiser_functions.py
index ab98113c..4b0d4b94 100644
--- a/recommendations/optimiser/optimiser_functions.py
+++ b/recommendations/optimiser/optimiser_functions.py
@@ -424,4 +424,4 @@ def check_needs_ventilation(
         x in property_measure_types for x in measures_needing_ventilation
     )
 
-    return needs_ventilation and not has_ventilation and ventilation_included
+    return needs_ventilation and not property_already_has_ventilation and ventilation_in_included_measures
diff --git a/recommendations/tests/test_optimiser_functions.py b/recommendations/tests/test_optimiser_functions.py
index 8f898970..debd2d88 100644
--- a/recommendations/tests/test_optimiser_functions.py
+++ b/recommendations/tests/test_optimiser_functions.py
@@ -143,7 +143,9 @@ class TestAddBestPracticeMeasures:
             ]
         }
         selected = set()
-        updated = optimiser_functions.add_best_practice_measures(property_id, solution, recommendations, selected)
+        updated = optimiser_functions.add_best_practice_measures(
+            property_id, solution, recommendations, selected, True
+        )
         assert "vent1" in updated
         assert "trickle1" in updated
 
@@ -273,7 +275,7 @@ class TestIncreasingEpcE2e:
         total_optimised_gain = sum(m["gain"] for m in solution)
         assert total_optimised_gain == 17.6, "Total gain of optimised measures should meet or exceed target gain"
 
-        selected = optimiser_functions.add_best_practice_measures(p.id, solution, recommendations, selected)
+        selected = optimiser_functions.add_best_practice_measures(p.id, solution, recommendations, selected, False)
 
         # Flatten recommendations for output
         flattened = optimiser_functions.flatten_recommendations_with_defaults(p.id, recommendations, selected)