diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index 9d9a7802..e2c295c2 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -830,7 +830,29 @@ class EpcPropertyDataMapper:
                 secondary_heating_type=schema.sap_heating.secondary_heating_type,
                 cylinder_insulation_thickness_mm=schema.sap_heating.cylinder_insulation_thickness,
             ),
-            sap_windows=[],
+            # ADR-0028: 990/1000 omit sap_windows -> synthesised from the
+            # glazed_area band + TFA (added in a later slice). The 10 rich
+            # certs keep their lodged per-window geometry.
+            sap_windows=[
+                SapWindow(
+                    frame_material=None,
+                    glazing_gap=0,
+                    orientation=w.orientation,
+                    window_type=w.window_type,
+                    glazing_type=w.glazing_type,
+                    # ADR-0028: the 10 rich certs lodge a real per-window
+                    # window_area (Measurement) -- use it directly as geometry
+                    # (width = area, height = 1.0) rather than the placeholder
+                    # windowless 0x0.
+                    window_width=_measurement_value(w.window_area),
+                    window_height=1.0,
+                    draught_proofed=False,
+                    window_location=w.window_location,
+                    window_wall_type=0,
+                    permanent_shutters_present=False,
+                )
+                for w in schema.sap_windows
+            ],
             sap_energy_source=SapEnergySource(
                 mains_gas=es.mains_gas == "Y",
                 meter_type=str(es.meter_type),
diff --git a/datatypes/epc/schema/rdsap_schema_18_0.py b/datatypes/epc/schema/rdsap_schema_18_0.py
index 4289aef7..08e008db 100644
--- a/datatypes/epc/schema/rdsap_schema_18_0.py
+++ b/datatypes/epc/schema/rdsap_schema_18_0.py
@@ -170,6 +170,19 @@ class RenewableHeatIncentive:
     impact_of_solid_wall_insulation: Optional[int] = None
 
 
+@dataclass
+class SapWindow:
+    """Per-window geometry. ADR-0028: only 10/1000 18.0 certs lodge this array
+    (all band-4); window_area arrives as a Measurement and is read via
+    `_measurement_value`. Mirrors the 20.0.0 SapWindow shape."""
+
+    orientation: int
+    window_area: float
+    window_type: int
+    glazing_type: int
+    window_location: int
+
+
 @dataclass(kw_only=True)
 class RdSapSchema18_0:
     uprn: int
@@ -258,3 +271,8 @@ class RdSapSchema18_0:
     sap_flat_details: Optional[SapFlatDetails] = None
     address_line_2: Optional[str] = None
     alternative_improvements: Optional[List[AlternativeImprovement]] = None
+    # ADR-0028: additive — the placeholder schema omitted sap_windows entirely,
+    # silently dropping the 10 rich certs' lodged per-window geometry. Capture it
+    # so the mapper can use lodged window_area directly (default [] = windowless,
+    # synthesised from the glazed_area band).
+    sap_windows: List[SapWindow] = field(default_factory=list)