diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index 51ab939b..8f55db80 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -1094,6 +1094,9 @@ class EpcPropertyDataMapper:
             # ADR-0028: sheltered_sides from built_form, else the calculator
             # assumes mid-terrace (2) for every dwelling.
             sap_ventilation=SapVentilation(
+                mechanical_ventilation_kind=_api_mechanical_ventilation_kind(
+                    schema.mechanical_ventilation
+                ),
                 sheltered_sides=_api_sheltered_sides(schema.built_form),
             ),
             # ADR-0028: total + low-energy OUTLET counts, not a bulb split.
@@ -1292,6 +1295,9 @@ class EpcPropertyDataMapper:
             # ADR-0028: sheltered_sides must come from built_form, else the
             # calculator assumes mid-terrace (2) for every dwelling.
             sap_ventilation=SapVentilation(
+                mechanical_ventilation_kind=_api_mechanical_ventilation_kind(
+                    schema.mechanical_ventilation
+                ),
                 sheltered_sides=_api_sheltered_sides(schema.built_form),
             ),
             # ADR-0028: 18.0 gives total + low-energy OUTLET counts, not an
@@ -1746,6 +1752,9 @@ class EpcPropertyDataMapper:
             # them via RdSAP Table 5), but sheltered_sides must come from
             # built_form — else the calculator assumes mid-terrace (2) for all.
             sap_ventilation=SapVentilation(
+                mechanical_ventilation_kind=_api_mechanical_ventilation_kind(
+                    schema.mechanical_ventilation
+                ),
                 sheltered_sides=_api_sheltered_sides(schema.built_form),
             ),
             # ADR-0027: 20.0.0 gives total + low-energy OUTLET counts, not an