diff --git a/datatypes/magicplan/domain/models.py b/datatypes/magicplan/domain/models.py
index 4dda8859..bbd4262b 100644
--- a/datatypes/magicplan/domain/models.py
+++ b/datatypes/magicplan/domain/models.py
@@ -1,4 +1,19 @@
 from dataclasses import dataclass, field
+from typing import Optional
+
+
+@dataclass
+class WindowVentilation:
+    opening_type: Optional[str] = None
+    num_openings: Optional[int] = None
+    pct_openable: Optional[int] = None
+    trickle_vent_area_mm2: Optional[int] = None
+    num_trickle_vents: Optional[int] = None
+
+
+@dataclass
+class DoorVentilation:
+    undercut_mm: Optional[float] = None
 
 
 @dataclass
@@ -7,11 +22,13 @@ class Window:
     height_m: float
     area_m2: float
     opening_type: str
+    ventilation: Optional[WindowVentilation] = None
 
 
 @dataclass
 class Door:
     width_mm: float  # TODO: should this be m or mm?
+    ventilation: Optional[DoorVentilation] = None
 
 
 @dataclass
diff --git a/datatypes/magicplan/domain/tests/test_mapper.py b/datatypes/magicplan/domain/tests/test_mapper.py
index 78977939..7632e7ef 100644
--- a/datatypes/magicplan/domain/tests/test_mapper.py
+++ b/datatypes/magicplan/domain/tests/test_mapper.py
@@ -225,3 +225,26 @@ def plan4() -> Plan:
 
 def test_plan4_address_uses_street_number_when_street_absent(plan4: Plan):
     assert plan4.address == "2, Bromley, GB"
+
+
+# --- New fixture: new-format API response with custom_displayable_fields ---
+
+NEW_FIXTURE_DIR = Path(__file__).parents[4] / "tests" / "magic_plan"
+
+
+@pytest.fixture(scope="module")
+def plan_new() -> Plan:
+    payload = json.loads(
+        (NEW_FIXTURE_DIR / "magicplan_api_plan_response.json").read_text()
+    )
+    return map_plan(MagicPlanPlan.model_validate(payload["data"]))
+
+
+def test_kitchen_window_has_ventilation(plan_new: Plan) -> None:
+    # Arrange — Kitchen is floor 0 room 0; its only window is a windowcasement
+    # with custom_displayable_fields populated in the new fixture.
+    window = plan_new.floors[0].rooms[0].windows[0]
+
+    # Assert
+    assert window.ventilation is not None
+    assert window.ventilation.trickle_vent_area_mm2 == 1700