diff --git a/datatypes/epc/domain/tests/test_from_rdsap_schema.py b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
index a8d5261f..a817414c 100644
--- a/datatypes/epc/domain/tests/test_from_rdsap_schema.py
+++ b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
@@ -2702,3 +2702,30 @@ def test_rdsap_mappers_carry_main_heating_controls_display(
 
     assert result.main_heating_controls is not None
     assert result.main_heating_controls.description == expected
+
+
+@pytest.mark.parametrize(
+    "schema_cls, mapper, fixture",
+    [
+        (RdSapSchema17_1, EpcPropertyDataMapper.from_rdsap_schema_17_1, "17_1.json"),
+        (RdSapSchema18_0, EpcPropertyDataMapper.from_rdsap_schema_18_0, "18_0.json"),
+        (RdSapSchema20_0_0, EpcPropertyDataMapper.from_rdsap_schema_20_0_0, "20_0_0.json"),
+    ],
+)
+def test_rdsap_mappers_map_mechanical_ventilation_kind(
+    schema_cls: Any, mapper: Any, fixture: str
+) -> None:
+    # Calc-facing: an MVHR cert (mechanical_ventilation=4) must reach the §2
+    # ventilation cascade as MVHR, not be silently treated as natural. These
+    # three build a bare SapVentilation(sheltered_sides=…) and dropped the
+    # top-level mechanical_ventilation; 17.0 + 21.0.1 + full-SAP already map it
+    # (via _sap_17_1_ventilation / their own wiring). 19.0 + 21.0.0 set no
+    # sap_ventilation at all — a bigger, separate gap (see followups). Natural
+    # certs (code 0/5 → None) are unchanged, so the fix only moves genuine
+    # MEV/MVHR certs (ADR-0037 follow-up).
+    data = load(fixture)
+    data["mechanical_ventilation"] = 4
+
+    result = mapper(from_dict(schema_cls, data))
+
+    assert result.sap_ventilation.mechanical_ventilation_kind == "MVHR"