diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index acf3c615d..4159bf658 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -9776,6 +9776,10 @@ _ELMHURST_MV_TYPE_TO_KIND: Dict[str, str] = {
     # picking which (25)m formula to apply.
     "Mechanical extract, decentralised (MEV dc)": "EXTRACT_OR_PIV_OUTSIDE",
     "Mechanical ventilation with heat recovery (MVHR)": "MVHR",
+    # PIV from the loft is treated as natural ventilation → (24d)m (per the
+    # MechanicalVentilationKind.NATURAL contract); only PIV from OUTSIDE is
+    # whole-house extract → EXTRACT_OR_PIV_OUTSIDE / (24c)m.
+    "Positive input from loft": "NATURAL",
 }