diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index ae8682b0e..5f9e72316 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -748,6 +748,11 @@ class EpcPropertyDataMapper:
             built_form=(
                 str(schema.built_form) if schema.built_form is not None else None
             ),
+            secondary_heating=(
+                EpcPropertyDataMapper._map_energy_element(schema.secondary_heating)
+                if schema.secondary_heating is not None
+                else None
+            ),
             dwelling_type=(
                 schema.dwelling_type
                 if isinstance(schema.dwelling_type, str)
diff --git a/datatypes/epc/schema/sap_schema_17_1.py b/datatypes/epc/schema/sap_schema_17_1.py
index 1f7754bb2..8a0b2220d 100644
--- a/datatypes/epc/schema/sap_schema_17_1.py
+++ b/datatypes/epc/schema/sap_schema_17_1.py
@@ -209,6 +209,10 @@ class SapSchema17_1:
     # gov built_form code (1 detached … 6 enclosed mid-terrace). Carried for the
     # property-details panel and exposed-side handling (ADR-0037).
     built_form: Optional[int] = None
+    # Lodged secondary heating element (description + ratings); "None" when the
+    # cert has no secondary. Read by the calculator's cert_to_inputs — dropping
+    # it under-counts a real secondary heater (ADR-0037).
+    secondary_heating: Optional[EnergyElement] = None
     # measured living-room area (m²); the engine consumes it via a back-solved
     # habitable_rooms_count (Table 27). Optional — 100% present in the corpus.
     living_area: Optional[Union[int, float]] = None