diff --git a/datatypes/epc/domain/tests/test_from_rdsap_schema.py b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
index f5077eac..49932030 100644
--- a/datatypes/epc/domain/tests/test_from_rdsap_schema.py
+++ b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
@@ -1637,3 +1637,37 @@ class TestRdSap18_0ReducedFieldSynthesis:
         # Assert
         assert result.incandescent_fixed_lighting_bulbs_count == total - low
         assert result.low_energy_fixed_lighting_bulbs_count == low
+
+    def test_ventilation_maps_chimneys_draughtproofing_and_sheltered_sides(
+        self,
+    ) -> None:
+        # Arrange — ADR-0028: 18.0 lodges open_fireplaces_count (else dropped),
+        # percent_draughtproofed, and built_form. Build sap_ventilation with
+        # sheltered_sides from built_form (else the calculator defaults every
+        # dwelling to mid-terrace=2). A cert with an open fireplace.
+        from datatypes.epc.domain.mapper import _api_sheltered_sides  # pyright: ignore[reportPrivateUsage]
+
+        corpus = _load_18_0_corpus()
+        if not corpus:
+            pytest.skip("no RdSAP-Schema-18.0 corpus harvested")
+        cert = next(
+            (
+                c
+                for c in corpus
+                if not c.get("sap_windows") and (c.get("open_fireplaces_count") or 0) >= 1
+            ),
+            None,
+        )
+        if cert is None:
+            pytest.skip("no corpus cert with an open fireplace")
+
+        # Act
+        result = EpcPropertyDataMapper.from_api_response(cert)
+
+        # Assert
+        assert result.open_chimneys_count == cert["open_fireplaces_count"]
+        assert result.percent_draughtproofed == cert["percent_draughtproofed"]
+        assert result.sap_ventilation is not None
+        assert result.sap_ventilation.sheltered_sides == _api_sheltered_sides(
+            cert["built_form"]
+        )