diff --git a/recommendations/Recommendations.py b/recommendations/Recommendations.py
index e470c1a3..acd49e05 100644
--- a/recommendations/Recommendations.py
+++ b/recommendations/Recommendations.py
@@ -768,6 +768,24 @@ class Recommendations:
 
                 # Update the current phase values
                 current_phase_values["sap"] = previous_phase_values["sap"] + property_phase_impact["sap"]
+
+            # This is very much an edge case but we also the end result taking the property
+            # below a SAP rating of 1, which is the minimum SAP rating
+            if previous_phase_values["sap"] + property_phase_impact["sap"] < 1:
+                sap_adjustment = 1 - (previous_phase_values["sap"] + property_phase_impact["sap"])
+                adjustments.append(
+                    {
+                        "recommendation_id": rec["recommendation_id"],
+                        "phase": rec["phase"],
+                        "sap_adjustment": sap_adjustment,
+                    }
+                )
+                # The new impact should be the current impact plus the adjustment
+                property_phase_impact["sap"] = property_phase_impact["sap"] + sap_adjustment
+
+                # Update the current phase values
+                current_phase_values["sap"] = previous_phase_values["sap"] + property_phase_impact["sap"]
+
         elif rec["type"] == "loft_insulation":
             # When we have a loft insulation recommendation, where there is an extension and the existing
             # amount of loft insulation is already good, we limit the SAP points
diff --git a/recommendations/tests/test_recommendations.py b/recommendations/tests/test_recommendations.py
index a9915422..e3bcbb2f 100644
--- a/recommendations/tests/test_recommendations.py
+++ b/recommendations/tests/test_recommendations.py
@@ -347,21 +347,21 @@ def property_instance():
     "input_data, expected",
     [
         (
-            [
-                {"recommendation_id": "a", "phase": 0, "sap_adjustment": 1.7},
-                {"recommendation_id": "b", "phase": 0, "sap_adjustment": 1.7},
-            ],
-            [{"recommendation_id": "a", "phase": 0, "sap_adjustment": 1.7}],
+                [
+                    {"recommendation_id": "a", "phase": 0, "sap_adjustment": 1.7},
+                    {"recommendation_id": "b", "phase": 0, "sap_adjustment": 1.7},
+                ],
+                [{"recommendation_id": "a", "phase": 0, "sap_adjustment": 1.7}],
         ),
         (
-            [
-                {"recommendation_id": "a", "phase": 1, "sap_adjustment": 2},
-                {"recommendation_id": "b", "phase": 2, "sap_adjustment": 3},
-            ],
-            [
-                {"recommendation_id": "a", "phase": 1, "sap_adjustment": 2},
-                {"recommendation_id": "b", "phase": 2, "sap_adjustment": 3},
-            ],
+                [
+                    {"recommendation_id": "a", "phase": 1, "sap_adjustment": 2},
+                    {"recommendation_id": "b", "phase": 2, "sap_adjustment": 3},
+                ],
+                [
+                    {"recommendation_id": "a", "phase": 1, "sap_adjustment": 2},
+                    {"recommendation_id": "b", "phase": 2, "sap_adjustment": 3},
+                ],
         ),
     ],
 )
@@ -1478,3 +1478,103 @@ def test_lighting_and_loft_adjustment_combined(property_instance, heat_demand_pr
         {'recommendation_id': '0_phase=0', 'phase': 0, 'sap_adjustment': np.float64(1.7)},
         {'recommendation_id': '4_phase=2', 'phase': 2, 'sap_adjustment': np.float64(4.0)}
     ]
+
+
+def test_mechanical_ventilation_sap_floor(property_instance):
+    rec = {
+        "type": "mechanical_ventilation",
+        "recommendation_id": "mv_test",
+        "phase": 1,
+    }
+
+    previous_phase_values = {"sap": 2.0}
+    current_phase_values = {"sap": 0.5}  # model prediction already below 1
+    property_phase_impact = {"sap": -1.5, "carbon": 0, "heat_demand": 0}
+    adjustments = []
+
+    updated_impact, updated_current, updated_adjustments = (
+        Recommendations._apply_measure_specific_rules(
+            rec=rec,
+            property_phase_impact=property_phase_impact,
+            previous_phase_values=previous_phase_values,
+            current_phase_values=current_phase_values,
+            adjustments=adjustments,
+            property_instance=property_instance
+        )
+    )
+
+    # SAP should be clamped to minimum 1
+    assert updated_current["sap"] == 1.0
+
+    # Original final SAP would have been 0.5 → so adjustment = 1 - 0.5 = 0.5
+    assert updated_adjustments == [
+        {
+            "recommendation_id": "mv_test",
+            "phase": 1,
+            "sap_adjustment": 0.5,
+        }
+    ]
+
+    # Impact should now reflect new clamped SAP
+    assert updated_impact["sap"] == -1.0  # 2.0 → 1.0
+
+
+def test_mechanical_ventilation_no_floor_adjustment(property_instance):
+    rec = {
+        "type": "mechanical_ventilation",
+        "recommendation_id": "mv_test",
+        "phase": 1,
+    }
+
+    previous_phase_values = {"sap": 5.0}
+    current_phase_values = {"sap": 3.0}
+    property_phase_impact = {"sap": -2.0, "carbon": 0, "heat_demand": 0}
+    adjustments = []
+
+    updated_impact, updated_current, updated_adjustments = (
+        Recommendations._apply_measure_specific_rules(
+            rec=rec,
+            property_phase_impact=property_phase_impact,
+            previous_phase_values=previous_phase_values,
+            current_phase_values=current_phase_values,
+            adjustments=adjustments,
+            property_instance=property_instance
+        )
+    )
+
+    # No adjustment expected
+    assert updated_adjustments == []
+
+    # SAP unchanged
+    assert updated_current["sap"] == 3.0
+    assert updated_impact["sap"] == -2.0
+
+
+def test_mechanical_ventilation_exactly_one_no_adjustment(property_instance):
+    # Test when SAP = 1
+    rec = {
+        "type": "mechanical_ventilation",
+        "recommendation_id": "mv_test",
+        "phase": 1,
+    }
+
+    previous_phase_values = {"sap": 2.0}
+    current_phase_values = {"sap": 1.0}
+    property_phase_impact = {"sap": -1.0, "carbon": 0, "heat_demand": 0}
+    adjustments = []
+
+    updated_impact, updated_current, updated_adjustments = (
+        Recommendations._apply_measure_specific_rules(
+            rec=rec,
+            property_phase_impact=property_phase_impact,
+            previous_phase_values=previous_phase_values,
+            current_phase_values=current_phase_values,
+            adjustments=adjustments,
+            property_instance=property_instance
+        )
+    )
+
+    # Exactly 1 → no adjustment
+    assert updated_adjustments == []
+    assert updated_current["sap"] == 1.0
+    assert updated_impact["sap"] == -1.0