diff --git a/etl/epc_clean/epc_attributes/RoofAttributes.py b/etl/epc_clean/epc_attributes/RoofAttributes.py
index 9e400235..ed2b4d07 100644
--- a/etl/epc_clean/epc_attributes/RoofAttributes.py
+++ b/etl/epc_clean/epc_attributes/RoofAttributes.py
@@ -138,4 +138,8 @@ class RoofAttributes(Definitions):
         if "insulation_thickness" not in result:
             result['insulation_thickness'] = None
 
+        if result["has_dwelling_above"]:
+            result["thermal_transmittance"] = 0
+            result["thermal_transmittance_unit"] = 'w/m-¦k'
+
         return result